BodyKits NW

Well I didn't know exactly what to put as the subject heading, but I wanted to get a conversation going about boost levels and torque.

Example 1. Here is one of my old dynos on my motor at about 10.5psi.


Now I know the low torque numbers is due to the amount of PSI I am running. I understand that the numbers are typical for the amount of PSI I am making 380whp on. Exactly why is that?

Another question I have is during one of my dyno sessions I actually increased the PSI level about 1.5-2psi, but horsepower was almost identical, but torque increased much more. Since I use boost comp the AF was right from my previous tune at 10.5psi. I can see that maybe it would want a lil more fuel, but even at 12.0 AF the only difference I saw on the dyno with the higher boost level was more torque. The horespower reading increased slightly if at all.

Now my other question about turbo size. If anyone has followed my lil projects I have tested quite a few turbo's these past few years. Mostly the 61mm turbos.

First turbo was the SC61, 2nd was Innovative SC61 Killer, 3rd was a GT35E, and now I am running the GT35R "Thank you Art, I know, I should have ran that from the beggining" But I have learned a lot in the process, and plus I don't like listenin to the hype these companies come up with. SC61 killer, Inconel wheel, GT Technology, our own compressor housings make more power. You know what I am saying. So I wanted to test them all myself.

Anyways all those 3 61mm produced basically the same amount of power. If I remember right the SC61 actually spooled the fastest.

Now maybe this is a stupid question, but I'd love to get a answer from you tuning guru's since you guys can explain it much better than I can.

Now I have never had a opportunity to tune any of the turbos at high boost due to the fact that my motor is pretty effecient and makes great power at low boost. I ain't tryin to push the pump gas limit and I am by no means here on honda-tech to say "hey I made 550whp on pump gas" that's not what I am trying to do.

Anyways the GT35R I now have is about 500-600 rpms laggier than any of my old 61mm turbos with the .63 AR housing. I was hoping to move to the S housing and .82 AR, and only see 200-300rpms of lag due to the ball bearing...obviously I was quite off on that assumption. At about 12.5psi I made 415whp on a street tune. I made 388whp@10.5psi on my GT35E, let's assume that at 12.5psi it made the same power, but with faster spool. Where does the GT35R truly shine? Will it start eating up the GT35e only at higher boost levels?

I really wish I could dyno the GT35r on low boost, but my spring won't let me. Cause I am dying to know if the GT35R is making more power at 10.5psi than my previous turbo...just being curious. But from my experience in the past, the PSI increase HP much at all. Why is that? How come the motor didn't for example make 35whp difference or anything crazy? Does it matter on the turbo, the compressor map? What is it? I guess you could not divide 388whp/10.5psi and get a horsepower number per psi. Cause that would come out to be 36HP per PSI and if that was right I would be making 900whp@25psi. So that obviously isn't going to work hahaha. Anyways, I am curious about all this, and if anyone would take the time to answer these questions from all my rambling that would be great.

BodyKits NW

Also what is the typical HP difference from going to a S housing and .82AR? If anything it seems like the power differece is only about 20whp, but more lag.

Also I know there is a formula for the above question. I think boosted-hybrid posted it awhile ago. Anyone care to post that formula and plug the numbers above to show everyone how to calculate it correctly to give them an idea where their torque numbers should be.

BodyKits NW

adseguy

HP = (torque * RPM)/5252

I think that's what you are looking for.

adseguy

You have low torque numbers because of the high revving you do. If you lower the rpm (I don't suggest it because you are still holding torque well to 9k) and keep the same HP you WILL get more torque according to the formula.

Remember, a dyno only measures torque and then calculates HP from that.

BodyKits NW

Yah that is the equation.

Now my 2nd question was, why did only torque numbers increase when I turned up the boost 1.5-2psi when I was running my older GT35E. Cause if that truly was the power output and horsepower did not change much at all, then clearly my GT35R makes more power than my older GT35E at the same boost level.

adseguy

Well peak torque happens kindof in the middle of the power band and peak horsepower should happen a couple hundred RPM before you stop revving (if your setup can handle the rev limit). This is because torque starts to drop off fast enough that revving it out more won't make you go faster....so you shift to come back into that bell shaped power band.

If your torque increased then so did your HP at the level assuming it happend at the same RPM....check if you wan tI guarantee it according to the equation . That's how torque can go up, but PEAK HP may not. Hope that covers it


Modified by adseguy at 1:38 PM 2/5/2007

BodyKits NW

I got lost. haha.

All I know is when I tuned for 10.5 psi, I turned up the boost to see what kind of power it would make at a higher boost level. When I turned it up 1.5-2psi I saw very very little change in horsepower, only in torque.

I am curious to why the horsepower did not increase like 15-30whp. I figured with the extra 2psi I would get a increase in poweroutput from the GT35E. This is all going to 9500rpms.

BodyKits NW

Ok, I read it over and I understand what you are saying. Wherever the increase of torque was, there should be a increase in horsepower in that same area. I understand that.

But even then, with more psi, why did not peak power not increase atleast 15whp or whatever.

adseguy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BodyKits NW &raquo;</TD></TR><TR><TD CLASS="quote">
But even then, with more psi, why did not peak power not increase atleast 15whp or whatever. </TD></TR></TABLE>

A few theories then:

Boost pressure the same through out the run (even until the end?)
Inefficiency of the turbo especially at high RPM
little variances in torque between each run can make HP numbers look goofy especially at high RPM...think of the equation
tuning?

Those are just a few reasons. don't worry you are going faster with more boost and you will make more peak power. How big the area under the HP curve is going to determine how fast you will go.

BodyKits NW

Well I am just tryin to figure out why that is. Because if that is true what I saw on the dyno, then it clearly shows that my GT35R outperformed my GT35E at the same boost level. I have yet been able to run the GT35R at 10.5psi due to my wastegate spring. But I do remember raising the boost to about 13psi with the GT35E, but only torque changed. I found that quite odd.

JDogg

if the boost is stable all the way out and only the tq changes then that means you have something holding the engine back up top. more boost should in a perfect world give an equal increase in tq (thus hp) from the onset of boost untill you stop reving it.. you gain more in the middle b/c at those rpms the IM, head, cams, exh manifold/turbine are not nearly as worked as they are in the higher rpms. sometimes the combination is very good for certian power levels, anything more and anything less just dosnt work as well. example... the last supra i did, made 650 on 20psi with a gt4201r. with just 8 more lbs of boost it picked up 300hp, after that it wouldnt make anymore power, there was a civic i did last year that made 355 on 8lbs of boost, it took 20 to make 475hp, the combo worked great at 8lbs, but sucked at 20.

Tony the Tiger

Is the GT35E the same turbine size and the same A/R as the GT35R? You may have reached or beginning to reach the limits of the turbo itself if nothing else has changed on your setup. If the GT35R had a larger turbine (both wheel and housing), right away, it will always outperform the smaller turbo at HP/PSI.

Peak power is nice, but remember, sizing a turbo is not about how much more HP you can make per PSI of boost. It's about reaching peak torque as soon as possible but yet able to hold it until your particular redline AND at your particular power level. Sometimes even a flat torque curve is not ideal because the fattest power under the curve wins. You'd end up being faster with a "hill" looking torque curve so that HP curve will stay nearly flat near redline. The car won't be super thrilling to drive because the top-end lacks pull, but per given WHP, it is the fastest.

It's easy to grasp the whole idea of turbo sizing. Whatever power you plan to make, you size the turbo for that. Everything in between such as turbine wheel trim and housing a/r is to tailor for your particular engine and tweak the curve. The biggest mistake is to choose a turbo size larger that your intended power goal. Guys often say "the smaller turbo would choke, etc.." Choking is at the exhaust side, and you can simply run a large turbine to solve that. That's why we have turbos that are well matched right off the shelf, and the GT35R will be the best damn turbo within 500-600 WHP. It's probably not going to choke until you reach the limits of the compressor, on a Honda at least.

So if you want to see the GT35R shine, turn up the boost Or rev high enough to make use of that compressor flow to the limits of your head and cams

JDogg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">So if you want to see the GT35R shine, turn up the boost Or rev high enough to make use of that compressor flow to the limits of your head and cams
</TD></TR></TABLE>

turn up the booster

tony1

Fuel and ignition happens relative to manifold pressure, it's very possible that it got too rich/lean or didn't have enough timing when the boost was turned up.

BodyKits NW

Thanks for the great info guys. I'm always learning something.