There has been a thread started by RR98ITR on transients, which I thought I would add too. However I decided to make a separate thread to be dissociated from some of the personality issues. I don't have a Ph.D. in child psychology, just in physics. I thought I might add a little scientific enlightenment to this hocus-pocus discussion. As I have started looking at the boards to gain info on modifying my type R as a track car day, I found out about HyTech headers and a few other things. Now the discussion in the other thread turns to transient response, and I thought: "let's investigate something scientifically verifiable". If one defines transient response as the time it takes the car to get from one corner's exit velocity (after gently mashing the orange, or was that the throttle) to the next corner's brake point velocity (min. to max. velocity for that track segment). In order to get some realistic numbers, I looked at the data from my data acquisition system (made by Race-Technology, you should get one!) used at Mosport while lapping in my mostly stock NSX last September.

It was my first time there and by the end of the day, I was lapping consistently at 1:46 or 106 seconds. For you ITR fans, Pierre Kleinubing laps the same track in his racecar at about 1:36, or 10 seconds faster than me. From the data acquisition system, while looking at the speed (mph) plot for one lap, I found that there are 5 segments on the lap where one is more or less full on the throttle, making more use of the engine than the tires. This is the part coming up that puts a gleam in Mario Thiessen's eye (the old Hockenheim track really got him going, max. throttle stuff!). I gave a label to these five zones based on the corner positions at the start and end of each zone. They are as follows, along with starting and exit speed for my NSX:

1) Corner 1 out to 2, 77 to 100 mph
2) Corner 2 out to 3, 85 to 96 mph
3) Corner 3 out to 4, 62 to 100 mph
4) Corner 5 out to 8, 40 to 128 mph
5) Corner 10 out to 1, 62 to 96 mph

The above are thus the transient sections where we will determine the time it takes to go from one speed to the other, and see how changing the power band, or area under the curve, affects the time. The astute among you will notice that there are some segments that appear to be missing, such as Corner 4 out to 5. But as Pierre Kleinubing said about the modifications to Mosport: " Four yussed to be flat, but iss flat no more". Also Corner 5 out to 8 is the main straight with 6 and 7 taken at full throttle. In order to determine the time for the segments, I could of course have just looked at the data acquisition plot, but this wouldn't allow me to see the effects of various engine power curves. I then made a spreadsheet model of Part 9: Straights, from the Physics of Racing Series. In order to check the validity of the predictions from this spreadsheet, which computes speed incrementally (at every 0.1 feet of forward displacement), the new speed point being based on the last speed and force now available, I entered data for a stock NSX and a stock ITR, assuming a 180 pound driver used for magazine testing is added to the weight. The results of the simulation are as follows:

Data:
Car weight Cd Area Tire dia. Diff Gears
NSX 3010 0.32 19.2 24.9 4.062 3.071, 1.727, 1.230, 0.967, 0.771
ITR 2595 0.33 20.5 23.9 4.400 3.230, 2.105, 1.458, 1.107, 0.848

I had to make educated guesses for the aerodynamic data for the ITR. It turns out the published frontal area for the NSX is 84.7% of its width x height, and so I used the same factor for the ITR, while for the Cd, I adjusted it to match the published top speed. This is however the only estimated data for the simulations.
The dyno plots for each car were found on the web and have a peak hp for the NSX of 241.6 @ 7500 RPM and for the ITR a peak hp of 161.9 @ 7750 RPM, which are both in the mid-range of dyno plots I found on the web for these cars.

Results of the simulation:
Car 0-60 mph 0-100 mph 1/4 mile 1/4 mile mph top speed
NSX 5.00 11.6 13.4 108.1 168.4
ITR 6.10 15.30 14.5 97.7 143.7

These results are very close to magazine test results for the NSX and good for the ITR except for the 0-60 time, where the model has no way of compensating for the poor grip of a front wheel drive car off the line, and so underestimates the time which in magazine's is in the range of 6.60 seconds. (we all know rear wheel drive drag cars are faster!). Let's assume the model is correct and gives the 0-60 time for a super pair of drag radials on the ITR. The model does use a launch RPM for the first data point, along with a shift RPM thereafter, the numbers being 3000 for launch on both and 8000 shift for the NSX and 8600 for shift for the ITR, along with a maximum “g” value for the tires of 0.92.

Having established some credibility (at least to myself) for the model, we now return to transients at the track. A small leap of faith is required here since I will use the speeds of the NSX as a modeling target for the ITR. A friend of mine in his highly modified (and lightened) ITR was running circles around me at Mosport (well not quite!) with a lap time of 1:43, or 3 seconds faster. Hey it was my first time. What we (or at least I) are interested in is lowering lap times. Thus for a bone stock ITR, we can use the model to calculate the time to change speed from each corner's exit speed to the next brake point’s speed, and add up all the times for each segment to see how much time we are on the gas, assuming that the same speeds from corner to corner for an NSX apply for an ITR. Then we modify the engine and see how much this time is reduced. I remember reading a book by Ross Bentley where he said something like "let's face it boys, races are won in the straights". The results from the simulation are:

Case # 1
Stock ITR Time (seconds)
1) Corner 1 out to 2, 77 to 100 mph 6.20
2) Corner 2 out to 3, 85 to 96 mph 1.20
3) Corner 3 out to 4, 62 to 100 mph 9.20
4) Corner 5 out to 8, 40 to 128 mph 30.00
5) Corner 10 out to 1, 62 to 96 mph 5.90
Total time 52.50

Thus from a lap of 106 seconds, half the time (about 53 seconds) is spent exercising the engine at close to max acceleration. ( I did not log throttle position, and I assume not all of those segments were exactly pedal to the metal). Now we start to modify the engine to see how this total time is affected by “area” under the curve. To resolve the age-old argument of torque vs. horsepower, I decided to modify the engine's dyno plot by keeping the changes in “area” under the hp curve constant. As the RPM in my data is at every 250 RPM, I first added 5 hp to 16 data points for a total "area" increase of 5x16 or 80 "area" units. I then added 10 hp to 8 points, starting at various RPM, and finally 20 hp to 4 points, also at various RPM, thus always keeping the “area” added constant at 80 units. These do not necessarily make for realistic engines, but it certainly demonstrates the effect of "area" under the curve and shows where you want the power for this particular car and track. Some people have posted that peak hp is a useless number (even engine builders I believe). This is obviously false since peak hp with proper gearing yields the car's top speed potential. I was able to verify that for the ITR, Honda chose exactly the right rear end ratio to get the maximum speed of 144 mph. Anything else gives a lower max speed. Now this may be important to Mario Thiessen at Hockenheim where the motors have enough grunt for those F1 cars to reach terminal velocity (around 350 km/hr!), but looking at the NSX's terminal velocity at the end of the Mario Andretti straight, one can see that it is nowhere near its achievable terminal velocity of 168 mph, since I only reached 128 mph. This is also not even close to the ITR's terminal velocity of 144 mph. Thus in the main straight, a long time is spent below max. RPM in top gear for either car. The optimum is to adjust the overall ratios (tire dia., rear end and gearbox) to maximize the use of the engine not just for the straight, but also for the overall time in all the acceleration regions. More on this later. The results for the 5 hp increase starting at 4750 RPM to 8500 RPM are:

Case # 2
ITR + 5hp Time
1) Corner 1 out to 2, 77 to 100 mph 5.90
2) Corner 2 out to 3, 85 to 96 mph 1.20
3) Corner 3 out to 4, 62 to 100 mph 8.80
4) Corner 5 out to 8, 40 to 128 mph 27.80
5) Corner 10 out to 1, 62 to 96 mph 5.70
Total 49.40

Thus we have reduced the time to 49.40 seconds from 52.50 seconds, or an improvement of 3.10 seconds. We would of course reach higher speeds on the straights, and have to adjust our brake points, but this is beyond the scope of this simulation model (or at least my time). This is a good improvement for 5 hp across the band. We now add 10 hp to the engine in narrower bands, staring at 4750 to 6500 RPM and moving this to the range of 6750 to 8500 RPM. Our top speed will of course go up, but where does the track say we want the power to get from the slow speed to the top speed for all the segments combined?

Case# 3 4 5 6 7 8 9 10 11
Start RPM for power boost 4750 5000 5250 5500 5750 6000 6250 6500 6750
Stop RPM for power boost 6500 6750 7000 7250 7500 7750 8000 8250 8500
ITR + 10hp Times
1) 1 out to 2, 77 to 100 6.10 6.00 5.90 5.90 5.80 5.80 5.70 5.70 5.70
2) 2 out to 3, 85 to 96 1.20 1.20 1.20 1.20 1.20 1.20 1.10 1.10 1.10
3) 3 out to 4, 62 to 100 9.00 8.80 8.70 8.70 8.60 8.60 8.60 8.50 8.60
4) 5 out to 8, 40 to 128 28.80 27.90 27.80 27.50 27.30 27.10 26.90 26.40 27.20
5) 10 out to 1, 62 to 96 5.80 5.70 5.70 5.60 5.60 5.60 5.60 5.50 5.50
Total 50.90 49.60 49.30 48.90 48.50 48.30 47.90 47.20 48.10
Improvement over stock 1.60 2.90 3.20 3.60 4.00 4.20 4.60 5.30 4.40

From the above table one can see that the improvement for a 10 hp boost with the same increase in “area” under the curve as for the 5 hp boost, we have an initial decrease of 1.60 seconds for a low RPM boost which is not as good as the 5 hp gain, but this steadily improves to a whopping 5.30 seconds (case #10) for the boost placed between 6500 and 8250 RPM, and then it decreases to 4.40 seconds with the 10 hp boost going to the very top of the RPM band. So this I think is categorical proof that "area" under the curve is somewhat a bogus concept. What counts is where that "area" is. The previous simulation might lead you to think that you want the power at the top of the RPM range, but this is not true for this particular car and set of track segments. Further insight is gained by adding 20 hp to only 4 RPM points. Obviously not a realistic engine, but it serves to illustrate the sensitivity of the time function to the location in RPM terms of the hp "area" boost, as in Time Gain=function(hp boost, RPM start, RPM stop, Cd, A, Rolling resistance, Tire dia., Diff. ratio, Gear ratios, mass, etc.) for a particular set of track segments. Since there are more cases possible here, I started at the same RPM but skipped over a couple of cases to keep the number of cases the same as for the 10 hp boost, in the interest of brevity. The results are as follows:

Case# 12 13 14 15 16 17 18 19 20
Start RPM for power boost 4750 5500 6000 6500 6750 7000 7250 7500 7750
Stop RPM for power boost 5500 6250 6750 7250 7500 7750 8000 8250 8500
ITR + 20hp Times
1) 1 out to 2, 77 to 100 6.20 6.20 5.90 5.70 5.80 5.90 5.90 5.80 5.80
2) 2 out to 3, 85 to 96 1.20 1.20 1.20 1.20 1.20 1.10 1.10 1.10 1.00
3) 3 out to 4, 62 to 100 9.20 9.00 8.70 8.50 8.70 8.80 8.80 8.70 8.70
4) 5 out to 8, 40 to 128 29.90 29.60 27.80 26.10 27.50 28.40 28.20 27.70 27.60
5) 10 out to 1, 62 to 96 5.90 5.70 5.70 5.60 5.60 5.50 5.50 5.60 5.60
Total 52.50 51.70 49.30 47.10 48.80 49.70 49.50 48.90 48.70
Improvement over stock 0.00 0.80 3.20 5.40 3.70 2.80 3.00 3.60 3.80

Here we get the best improvement of all for case #15 of 5.40 seconds. However this time the function does not have just one minimum time, but two since after case #15 the improvement worsens to 2.80 seconds for case #17 but improves again going up to 3.80 seconds for case #20, where our 20 hp boost is at the very top of the band. When I ran this simulation, I was quite surprised at the results, for it shows that this car on this track the time is most sensitive to power in the 6500 to 7250 RPM band for the 20 hp cases, with another improvement between the 7750 to 8500 RPM band. This tends to match the best result for the 10 hp boost which gave a 5.30 second improvement for case #10, which at 6500 to 8250 just happens to encompass (well almost) the two best RPM bands for the 20 hp cases.

While looking at the simulation results, one can see that the bulk of the improvement in times is always for the long straight:
For the stock ITR, the straight time is (Case #1) 30.00 seconds.
For the 5 hp boost (Case #2) it is 27.80 seconds, accounting for 2.20 of the 3.00-second improvement or 73%.
For the 10 hp boost (case #10) the straight time is 26.40 seconds, accounting for 3.60 of the 5.30-second improvement or 68%.
For the 20 hp boost (Case #15) the straight time is 26.10 seconds, or 3.90 of the 5.40-second improvement or 72%.

As has been said before, races are won in the straights, the long one in particular. This of course assumes one has maximized the use of the tires in both braking and cornering (the subject of another simulation involving the driver no doubt). This observation allows us to then optimize the overall gearing for any particular case. A stock ITR is going 123.1 mph at 8600 RPM in 4th gear, thus it almost never gets out of 4th gear at Mosport, since the maximum speed we are assuming is 128 mph. It might not ever get that high, as the NSX did, since it takes 6.30 seconds and a very long 1143 feet to go from 123.1 to 128 mph in 5th gear. I could have done a slightly more realistic simulation using distance instead of feet because distance counts, since when you run out of track, well, you run out of track, but I thought most people relate more to speed in mph. What is the first question someone asks you when you tell them you drive on the track? However some people like old Ferry Porsche thought that the standing kilometer time was an interesting figure. My simulation says a stock ITR does it (3281 ft) in 26.4 seconds at 122.5 mph. It also takes 156.8 seconds to very slowly inch its way up to its terminal velocity of 143.7 mph in 30,073 ft, or about 5.7 miles. Now that is a long straight. How fast have you ever gone in your Type R? Since we are never gonna get there, what is the best diff. ratio to use (assuming you could change it) to minimize the times for our examples? I ran the simulation while varying the diff. ratio from the 4.40 stock value for Case#1, 2, 10 and 15 to see how much more we could optimize. The results are:

Case # 4.40 diff. time "best" diff ratio "best" time improv. Straight time
1 52.50 5.30 48.90 3.60 27.40
2 49.40 5.20 46.40 3.00 25.80
10 47.20 5.30 44.20 3.00 24.40
15 47.10 5.20 44.50 2.60 24.80

This shows there are very big gains to be made by optimizing the overall gearing between the engine's crankshaft and the tire contact point. Wish we all had Hewland gearboxes! I think there is a 4.785 rear end for JDM ITR's. However this does not mean that just going up in ratio maximizes the time. It turns out that for Case #1, changing the diff. to 4.10 reduces the total time to 50.10 seconds for a 2.40 second improvement, since it makes better use of 4th gear for this track. If you can't change the diff., you can change the tire diameter. Going from the stock 195/55/15 to a 225/50/16 like the old Realtime cars(dia. of 24.9 in.) gives a total time of 50.30 seconds for Case #1, an improvement of 2.20 seconds by effectively going closer to the 4.10 diff. ratio number. Going up to 225/45/17 (like the Realtime Cars) gives you a time of 50.00 seconds or 2.50 seconds better. Now this change is of course more controversial, since I have not modeled the inertia of the tire/wheel combo, and thus my simulation overestimates the potential improvement from changing tire size to change gearing. It just gives something else to think about (or simulate?). I believe in fact the Realtime cars use the 4.785 diff.

Back to transient response, torque and hp. If you think that the time to mash the throttle from corner exit part throttle to full throttle is significant compared to time spent in the main straight, then I suggest you buy some of that transient magic stuff. (I personally try to mash the throttle as soon as it feelsa good). As for me, I will try to get power in the right part of the band and work on overall gearing. Concentrate on the transient from straight entry to the straight brake point, and forget about the fractions of a second it takes to push the pedal down. And torque or hp? Well hp and RPM becomes torque (or was torque?), torque and ratios and tire radius becomes force, add mass and then Newton takes over, as in F=ma. Integrate the whole mess (he invented that too) and you get lap time. Physics rules!!!!

 

That's what I said too.

 

wow thats alot of info

 

Wow...a little too much for me this early in the day...need to look at it again once I'm fully awake...long weekend .

 

i fell asleep on the 2nd paragraph.....

 

Well the problem is that this was how transient response was defined in that other thread but never how it was defined by the people who defined the term originally.

Thank you for the good on-track analysis, and for leaving the personal baggage at home.

 

Wow...Very thorough article. Thanks!

 

Thanks, ... time to print and read it at home.

I'm also interested in that data system as well. Ed

 

my eyes, my eyes!! arrg...


j/k, took a brief look, not in mood to digest that much text right now. a quickly glance looks to be thoughtful. for effort at least.

transient reponse is a real thing. there hasn't been a lot of documentation on it though.

 

Holy ****, I had a headache before I started reading, gonna have to come back to this later

 

So this thread has nothing really to do with TR and all its' possible definitions from RR98ITR's thread??

Good information, I think I ought to read it again, and again. Thanks for all the time and thought you put into testing and explaning the data.

 

Yes, thank you for leaving the infantile antics behind.

But, I think you were needlessly confrontational with the following:

Also, I found your post to be long winded and inconclusive. I wish you had provided more data and hadn't tried to ram your conclusions down our throats. Also I found your whole presentation to be delivered in a condescending tone - which really offends people like me. Why couldn't you have been more Socratic?

But, having said that, I think your post is really neat, and I look forward to writing a follow up post that suggests that I actually understand it. You'll have to bear with me in the likely event that I try to turn it all into a giant tar ball.

Scott, actually a 72 year old woman who play acts with young men on the internet...."I get off on getting them all worked up, and I look at Transients like this: it's not the size of the boat, it's the motion of the ocean".....peace....

BTW - Does anybody think that 5hp across the band is going to add up to 3 seconds....I haven't really looked at this post closely but if that's so then there may actually be something to the idea of Transient Response, because such an effect appears unreasonable (fails the test of reasonability that is).

Seriously - whoever you are (Descartesfool), thanks for putting in the effort, I'll look at your work tonite....


[Modified by RR98ITR, 1:30 PM 2/3/2003]

 

Just re-read the whole thing and I find it to be very helpful in determining the features or characteristics associated with fast, and faster lap times.

I found the "tone" of the presentation to be very factual and well groundred, as well as easy to understand (though I am an Engineer ... BEEE).

This also points out the benefit(s) of good emperical data as supplied by data logging, and the need to carefully "digest" that which you've recorded.

This also suggests to me, the benefits of more power, especially down the straights where passing needs to be done in race conditions.

This, however, does not prove the advantage of a "transient response" as I believe it was suggested and used in connection with the hytech (sp) header design philisophy. Ed


[Modified by zygspeed, 8:26 PM 2/3/2003]

 

I need to look this over some more also. I'm still digesting a big dinner.

But,

2) Corner 2 out to 3, 85 to 96 mph 1.20

I don't think this will happen in a stock or a modified ITR. Your talking an 11 mph difference equal to the 40-50 or 50-60 range but here we are 85 to 96 which have much higher aero loads.

BTW, I should be posting something on this as well after I've compiled some more information.

 

Uh, Ed, had not such benefits occured to you before now?

How fortuitous then that your turbo will give you THAT too!

Scott, who HATES passing faster cars in T9/12 (corner before the longest straight at PIR)...."if I can just jump on close enough as they go by I can get enough of a tow........not"....

 

Of course it has/had, Scott.
That's why I ran a 4-1 header and a Mugen ECU!

Of course, boost will help ... one of these days I may even put a cage in the car and race it "like normal people with my affliction".


[Modified by zygspeed, 8:59 PM 2/3/2003]

 

Very interesting. It's good to have yet another perspective on the subject.

I'm not sure I trust the model, although that is the only way to eliminate other factors one would encounter in a real-world test, such as weight transfer and its effect on available grip when exiting corners (which is, after all, the place where the importance of "transient response" is supposed to be in question).

To summarise my own, rather insignificant opinion of the transient response issue, I don't see it being an area in which the stock motor requires concentrated efforts at improvment. While there may indeed be some very small flat spots in narrow bands of the usable rpm range, they do not seem to significantly hamper the engine's ability to accelerate. Build a well-balanced engine with a flat torque curve and sufficeint top-end power and you shall have a car that does very, very well on the track. This is easily possible with the B-series motors.

 

Ok, we're all sick of the subject, but Whathisname Descartesfool (I'm gonna call him Df unless he reveals himself to be.....Brian Beckman) has obligated us to give his presentation serious attention. Since I'm thru waiting for someone else to go first here goes:

First, I find it interesting that Df chose to approach the subject from a Data Logging perspective. If he really is a Ph.D. in Physics, which I say only because he is unidentified and we have only his word on that, I might have expected a little bit more than that last paragraph to deal with the fundamentals. I further might have expected a decently expressed narrative approach that succinctly got across the message in far less space and with far less work (and faith) demanded of the reader.

Strictly speaking, we all care about Time to Distance. With the typical core data acquisition package (no more than one beacon) you're stuck with nothing to work with (for this purpose) but speed, rpm, and time. Useful surrogates. Good enough? Yes. Df's characterizations differ from calculating time from Speed A to Speed B, and while that bothers me, it's not a material problem. Calculating time with respect to fixed speed values is suitable for the purpose of evaluating power changes.

Note that Df isn't using actual data logged in real life. He says he's constructed a spreadsheet model using the basics of physics as represented in "The Physics of Racing" - Part 9. Ok, no problem there. We do have a shift or two between corners 5 and 8, so I'm not crazy about that one - we should be looking at WOT in one gear at a time.

I find a couple of things to argue over in Part-9 itself: shifting at the torque peak... and modeling at constant torque - lead to "arificially good times and speeds". This is kinda messy.

We're missing Df's calculations, but the idea that he has pursued - demonstration of the effects of the distribution of horsepower along the powerband (which differs from my demonstration of the effect on horsepower of the distribution of torque (at equal total area) along the powerband) is intuitively interesting.

His post doesn't show us the distribution of our time along the powerband in his model explicitly, but his "improvement over stock" tells "a" story about that. The unknown accuracy of his model should caution us with regard to his results and conclusions. A thorough analysis of his model would require more information from Df, and is likely beyond the limits of my desire to grade papers anyway.

His results and conclusions are similar to my own inasmuch as he recomends the subordination of the distribution (inasmuch as that is practical/possible) to the requirements of particular tracks.

Remember when I wrote about "the area under the curve and the shape of the curve"? Same thing.

His comments on the usefulness of gearing are indisputable, but optimal gearing is beyond the means of most of us. I don't know that the Quaiffe and Hewland Transverse boxes are quick change anyway - doubt it.

His argument is essentially that horsepower moves a car down the track, and that what he understands this transient response stuff to be is hocus-pocus / magic, as opposed to his milieu - Physics. I'm interpreting that then as a negative judgement rendered against the cult of Transient Response.

While I'm sypathetic to Df's conclusions, and I appreciate his participation, I really don't feel he pushed us ahead meaningfully. I persist in thinking that the fundamentals of Force, Work, and Power tell the story most effectively to anyone capable of understanding. I wish Df would take the time to write a couple of paragraphs at that level - and deal convincingly with the old Torque vs Horsepower confusion.

Scott, who says that if any cult member wants to renounce their belief in the existence of something mysterious that propels a car down the road faster - other than Force, Work, and Power - it's never too late.....

 

Sharp eyes Dave. It's nice to see that someone was actually looking at the numbers! There was indeed an error in my spreadsheet model for the second acceleration zone going from 85 to 96 mph. I made a typo and had entered 90 mph instead of 96 mph, so those 1.20 to 1.00 second segments for the various cases would be for 85 to 90 mph. I corrected my mistake (I sometimes make some) and put in the correct 96 mph in the lookup function, and now the times for this zone are in the range of 3.10 to 2.70 seconds. If any one wants, I can repost the times, but none of the trends in the result change, only the total time is longer, with more room for improvement since it is easier to make a dent in the 3.10 than in the original 1.10 second sector time. The optimum rear end ratio also changed to about 4.9 due to this change.

I also recalculated all the times with a reduction in the maximum grip available for forward traction to a more realistic 0.44g instead of 0.88g, since a tire can't make much more forward force than it has vertical force acting on it. During acceleration, half the weight (round figures here) of the car is on the tractive tires (except for Mike Galati in his Audi, gotta love those starts!), and thus the tire can only provide a forward force equal to its load, or about 0.5g. For a 2600 lb car, with a 60/40 weight split (neglecting load transfer when you put the hammer down) 1560 lbs rest on the tractive tires and thus the tire gives about 1373 lbs of forward punch (for a tire capable of 0.88 g) and thus the car's accelerating g value is 1373/2600 or 0.53g. A stock ITR can provide more force than this than this in the lowest gear, and thus the reduction to 0.44g (to account for some tire slippage too) reduces the 0-60 time to 6.60 seconds from my original 6.10 seconds, matching the test data from the 1997 article in Car & Driver magazine. It also of course slowed down all the other times, including 1/4 mile to 15.1 seconds, but does not have much effect on the transition times used for the sectors, since these don't involve 1st gear. For more insight, see the first few articles from Brian Beckman's series at:

http://phors.locost7.info/contents.htm.

Results of the new simulation:
Car 0-60 mph 0-100 mph 1/4 mile 1/4 mile mph top speed
ITR...6.60....16.10......15.1.......97.1......143. 9
Car & Driver test values
ITR...6.60....17.90......15.3.......93.0......143. 0

So the model is close, but by no means perfect. As RR98ITR points out, there are simplifications with Part 9, Physics of Racing. I modified the model to shift not at the torque peak but at a user (me) selectable shift RPM, constant for all the gears, which was 8600 RPM for the ITR. Changing this changes all the times. Brian Beckman actually says he shifts at the torque peak of 4200 RPM for his article, but puts the torque constant at 330 ft/lbs for all RPM (Corvette!), so it is like he is shifting at a redline of 4200 RPM since the torque doesn't vary. In my model, I do not use a constant torque, but I use the actual hp vs. RPM (dyno plot) at every 250 RPM in a table, convert it to torque and the VLOOKUP function in Excel to interpolate the data for the actual RPM which the car's velocity and gear determine the engine is turning at for any data point. i.e. at 60.10 mph in 2nd gear the engine is turning at 7982 RPM, which is between my hp table points, and so the need for the VLOOKUP function.

I also did not include a time to shift gears because of laziness, and thus the numbers are not perfect. It is also difficult to model the change between sliding and non-sliding friction of the tires as one modulates the throttle off the line to get the best time between engine bogging down and tires slipping. In the absence of data logging for drag racing, I do not actually know how this progresses in reality. When the snow melts here, I will put my data logger into both my NSX and ITR and look at the engine RPM, throttle position, wheel RPM and speed to see how messy it all is on some acceleration runs. Maybe I'll even heat up the tires first. Then again maybe I could try it in the snow!

And as I mentioned in my 1st post, it would have been better to use an exit speed at each corner and calculate the time to reach the brake point in terms of distance and not speed, as pointed out. However as one changes the power of the engine, one's speed increases and one had better brake earlier. Thus an even more realistic simulation would work back from the end of the brake zone to get the slow speed, work back at maximum brake g's to find the brake point at the new higher end of straight speed, adjust the distance to be travelled down the straight and solve for the actual new brake point based on new speed. This is a little more work. However none of the conclusions would change. I also think working in only one gear is only of academic interest, and it is uch more interesting to see the effects of the engine transitioning from one speed to another by going up the gears. I like to shift up the straight. Just wish I had more power!

By the way I of course could not use data acquisition for the simulated engine, since I don't have the simulated engine. I did however have all the time's, g's, distances and as many track markers as I want without a single track beacon since my system uses a GPS to log position at stepped time intervals. It thus computes the track map by combining GPS and accelerometer data, and one adds track markers in software to compute any number of sector times, no lap beacons at all. It took the NSX about 23 seconds to go up the straight! Proof that it is worthwhile to research one's purchases.

Sincerely,

Claude Fortier, Ph.D. (I am now identified!, but I sort of like Df)
a.k.a Descartesfool

 

Dear Sirs ... I believe we have completely side-stepped the issue in the topic line, of "transient response" as espoused by HyTech (or whatever the name is), as it relates to the relative merit of his header design.

With respect to the inclusion of a shift or shifts in the data, ... it would seem that this it in the realm of the "transient response" noted by John, and would seem to be mostly a function of the choices made in designing the header (and tuning). John has not addressed the desirability of gearing, whereas it is now obvious that gearing plays and important and primary factory in getting the most out of a given car wrt lap times at any particular track.

For instance, the runoffs at Mid-Ohio and the longish downhill back straight.
Many of the GT-4 competitors have opted for numerically higher gearing for better acceleration around the rest of the track, but then seem to literally hit the wall and get passed down the back straight simply because they ran out of gearing ... but I too digress.

First we need to define the right question or problem (transient response wrt header design), then we can attempt to answer said question and/or solve the problem in a manner which makes sense not only in terms which everyone can understand, but which are also directed to the issue at hand.

Was there something in one of John's post about "transient response" having to do with some type of "recovery" aspect and on/off WOT?

Ed - how has been out of school for quite some time and doesn't appreciate being treated as though "his paper needs to be graded", when the instructor is in the wrong classroom.

 

Hmmmm.

So answer me this.....Claude Fortier, Ph.D...... if you would:

Well, sure more horsepower made the car go from A to B faster, BUT

What if it didn't?

And what if it went faster with Less Horsepower?

Those are the legs the cultists have stood their TR on.

Would you care to address these ideas more explicitly?

Sincerely,

Scott, who has deferred purchase of a data acquisition package so long he's lost interest.....the madness has to stop sometime.....I mostly like to drive.....

 

Ed,

I hope you're not offended - I meant no offense to anyone with that comment. It is an appropriate characterization of the type of effort required to evaluate Df's writing.

As to Johns On/Off Throttle TR, I think both Df and myself HAVE addressed that. I said that if there was a bunch of laptime tied up in that small interval, then the motor would likely rip itself free and run off down the track without me. I was using colorful language, but the characterization is apt - UNLESS John's purported benefit only adds up to a hundredth over a 30 minute race, in which case true or not who gives a ****. Df's reference to where you spend your time is essentially making the same point - though more quietly.

Scott, who always knew gearing was important....no point making more power higher in the rev range if you can't optimize your gearing to take advantage of it....

 

What if gravity made things go up instead of towards the center of the Earth ... it DOESN't!
If a vehicle went faster with less horsepower, then other limiting factors have changed, such as frontal area/drag, tires, and/or driving style (better driver). Hell, maybe they weren't using the chicaine!

Data acquisition is a good thing, as long as one can make use of it, and apply the knowledge gained to making appropriate changes to driving style, and vehicular improvements.

No problem Scott, I'm just trying to get in the mood to reject a few patent applications this morning, and this is good practice!

BTW -- gearing ... 6 or 7 speeds would be nice and fill in the gearing holes a bit better.
CVT's just don't seem to be able to hold the power and torque needed in racing conditions, but they have progressed tremendously in recent years.

I've got to do some work ... later Guys, been fun. Ed


[Modified by zygspeed, 11:13 AM 2/5/2003]

 

Not so fast there Ed....we've got a hill round these parts where the cars actually roll uphill! So much for you Theory!

Scott, who is wrapping his head in foil right now to keep the alien mind control waves from making me consume Canola Oil......

 

I really hate to go on and on and on, but something has been bugging me.

The other night I spent a fair amount of time looking over acoustics texts in search of information on "finite amplitude waves" as described in the Desktop Dyno book. Found nothing whatsoever, though strictly speaking I'm not supposed to expect to find anything on that under sound. Maybe if I search old NACA archives I'll find something. What's most troubling is that "Kadenacy" which that author says was discredited in the 40's, is still promulgated by those recommending Smith & Morrison.

Anyway, I also looked over the section on Fluid Mechanics and the especially big handbooks on CFD - Computational Fluid Dynamics. You may recall John Grudynski claiming CFD as the basis for his superior designs and execution - this was in his now most infamous H-T post. He also mentioned Fluent - Creators of CFD modeling software and Consultants in the field. Their home page displays their links to the world of automotive design and motorsports.

I think I found a helpful reference on their site that may shed light into Johns design process: http://www.fluent.com/about/news/new...00v9i1/a15.htm

Scott, who wonders if Ricardo offers the same Suite.....