I have two B series engines that was built at different times, and with slightly different compression and intake/exhaust. Both are extreme NA setups.

Setup A is using the R plenum and standard type R TB, while the other is using ITBs, and a bigger header, everything else is similar.

The strange thing is, one engine makes about 20hp less than the other, but that's kind of expected due to slight differences in setup.

What I'm curious about is how the heck did the engine make more torque before VTEC than after?

It's making 301Nm on the HPI dyno at 5288 rpm, while vtec point is at 6K.

Something seems to be very wrong here. I'd like to blame the ignition settings, but the tuner was someone brought in from Japan.

I'm used to seeing peak torques post vtec.

Any ideas?





Modified by shiroitenshi at 7:07 AM 11/24/2007

 

sorry for the camera dyno scans, I'm at a place where there isn't a scanner.

 

no one with ideas? What does ITB's improve on, actually, mid range, or top end? what does the length of the trumpets affect?

 

 

What's with the ?

 

jdm tuner...where are you located

 

were your camshafts properly degreed?, whats your cam gear settings?

 

Located in Malaysia.

Those are custom B20B setups. Not an oem part in them except for the block & head, and for the first setup, the original R intake manifold.

Yeah, the camshafts were degreed properly.. these are high comp setups with high duration cams, I don't think I'd be posting here if it were degreed improperly.

the limit allowable due to clearance is only 1-2degs.. that's the most, even that is too low in terms of clearance numbers but it seems to only like the exact same specs that was on the cam sheets gave good power.

About the peak torque.
I think it's because the HPI dyno doesn't do smoothing, because when I smoothed them out by averaging the numbers, I saw the peak being at 6.5K. Could be a dyno spike, I think. but the fact that it has held that torque for quite a range makes me think it's not a spike.

Does anyone have experience with the HPI dyno? I'm wondering if it has a smoothing function like dynojet's, coz I'm gonna get another printout from them if they do.

That 13 hp is also a spike, I think. because it seems to hover about 300hp from what I'm seeing. It seems to have characteristics of one, since it's only a single dot, unlike the pre vtec peak torque area.

Those jaggies make it difficult to see the actual peak. It's written there as 5.2 peak, but when I marked each rpm point and smooth out the curve, it seems like 6.5 is the actual peak. I don't really know.. kind of got used to looking at smoothed out charts... lol.

Now I've got to figure out how this second setup makes more than the previous one.
a) intake? ITB vs. Plenum
b) exhaust headers (muffler and piping are the same?)
c) cams?

In terms of compression, the previous setup a has slightly more, but the peak torque is at 7.5K.

but so far, the midrange on this is fairly thick. about 20-40hp gains on the midrange, and only 10-20hp on the top end. I think it's the ITB, but I'm not sure.

Anyone using ITBs for input on how ITB affects your power?

 

can you post both complete setups? and power graphs for both then we can offer our opinions

 

Setups

a:
Custom bore, stroke and rod lengths with custom forged pistons.
Intake - the same thing you'd get of a JDM type R with 2mm overbore.
Header - Custom
Exhaust/Muffler - Custom

I'm wondering if I should even post the measurements, because HT people always rag on small sizes, something about inadequacies, I guess.

Just say that the exhaust/muffler setup has smaller piping than what most 2L people are using here

b:
Custom bore, stroke and rod lengths with custom forged pistons.
Intake - Toda quads
Header - Custom (different from setup a with a slight increase in pipe diameter.
Exhaust/Muffler - Custom

Dyno chart, later. I don't have a scanner. I could generate one in excel with the dyno numbers though.

 

TQ = Cylinder Pressure

That statement alone, if you investigate it, should lead you down the path of why your TQ peak is pre-VTEC. Im guessing youre not running a ton of stroke in that thing.

What kind of fuel is this run on? Static CR?


Modified by Combustion Contraption at 12:43 PM 11/25/2007

 

Actually it is a big stroker, no short strokes can generate 210Nm (155lbs-ft) at 2K rpm.. no?

It's run on 97RON (malaysian standard), I think the premium 95 over at your place?

Possibly could make more than that on race fuels.

The first engine is similar, but the only difference is ITBs, the cams are only like a few degrees apart from the first setup, with similar lift, and based on visual check of the profiles, quite similar (the setup a cams are no longer in stock, and has a long waiting time if wanted the exact same grind, so had to make do with alternatives)

Makes me think it's the ITBs, as I think bigger headers give better peak if the size is increased. That's why I want to know what ITB users are getting out of their setups, esp. if they were using plenum setups before..

Simple to say, TQ = cylinder pressure, but cyclinder pressure = ignition timing/ring seal/head gasket seal, valve seat seal, etc. etc.


So far, it's not leaking, so it's possibly the ignition timing, but I don't think the japanese tuner was so idiotic not to try higher ignition timings.

But I think you forgot, TQ = stroke, and the primary problem of running big strokes has always been clearances, deck height, and side loading, but it's one of the core formula of getting low end grunt.

 

Sorry, i meant to put the smiley after the stroke comment to indicate i was being sarcastic. One of the reasons your TQ peak is pre-VTEC is because of the fact that its a large stroke. If displacement is kept the same, and you just alter the bore/stroke combo, all stroke does is shift the TQ peak around.

TQ doesnt = stroke, TQ = displacement. (and also cylinder pressure ) But, trying to keep this away from becoming a "theory" thread, you asked earlier what the effect the ITB length had. You seem to be knowledgeable about your setup, so im sure you know the generic rule about the longer the runners, the better the low speed TQ, the shorter, better for high speed HP. Well, i can tell you, ive tested it, and its held 100% true, even for our DOHC Honda's. On my personal test, i lost 10-13hp by lengthening the ITB's about 3.2". TQ peak was shifted down about 700rpm.

 

You guys consider running a engine sim?

 

You're right, TQ doesn't 100% = stroke, but it does play a part in increasing displacement and the low end torque.

Hmm.. long runners low end torque eh? The runners are pretty short, but the trumpet length is about 3". Considering the total length, that seems to hold true.

Been running plenums all this while, only recently started messing with ITBs.

surprised with the low end - midrange grunt of ITBs, because kind of thought they were offering better throttle response, since the opening rate of the butterflies are a lot larger than single throttle bodies.

Well third setup coming up, now going with less stroke and higher rpm and see what happens.

 

Engine sim? but the unpredictability is what makes building engines interesting, you compare it with what you know, and when you make more than you're supposed to... smile!