How dyno numbers are utilized by ITAC

[Chip42]

the GSR has a nice low-slope hp curve and a very flat torque curve. the P72 cams,head, and intake combo is designed for that. You'll see peaky power on the B16/17/18C5 due to the P30/whatever head, cams, and those intakes being better for building HP. the P72 intake, in particular, is restrictive to building peak hp.

I don't think 125% on a GSR is likely, but I think it makes up for that in large part due to the overall package and wide power curve, and really good driving.

[seckerich]

Irish Mike ran a 10/10ths E46 with us before going to ITR. It could be beat and Mike is a top notch driver so that is a fair data point.

[JeffYoung]

This is ITS Jeff speaking, not ITAC Jeff.

I don't buy it. Zsolt's car has more top end (both from personal experience and from watching his in-car data) than any other ITS car I've seen. Note I don't think the car is misclassed or anything, and I don't think it needs any adjustment.

But I think it makes really good power, and significantly more than 170. It's aero is good, maybe best in class, and that may explain the 125 mph+ advantage it has, but I'm personally convinced some of it is power.

I think all of the good S cars (other than the Miata, which is at a lower weight) are in the 170+ range.

I know that when I was making 160 whp or so, I couldn't compete. The jump to high 170s/181 was a big deal and changed the game. The three GSRs I've seen seem to be in "top ITS car" power ballpark.

Steve, forgot IMike ran that in S. Before the time where I was competitive, so I probably only saw him when lapping me.

Bottom line to me is there are a number of cars that can win in S (240z, 260z, 280z, 300zx, E46, E36, E30, Porsche 944S, TR8, Miata, RX7, Corrado). GSR is one of them.

the GSR has a nice low-slope hp curve and a very flat torque curve. the P72 cams,head, and intake combo is designed for that. You'll see peaky power on the B16/17/18C5 due to the P30/whatever head, cams, and those intakes being better for building HP. the P72 intake, in particular, is restrictive to building peak hp.

I don't think 125% on a GSR is likely, but I think it makes up for that in large part due to the overall package and wide power curve, and really good driving.

[Chip42]

Bottom line to me is there are a number of cars that can win in S (240z, 260z, 280z, 300zx, E46, E36, E30, Porsche 944S, TR8, Miata, RX7, Corrado). GSR is one of them.

on this, we agree.

[gran racing]

and that may explain the 125 mph+ advantage it has

What about 0 - 125 mph? Hey, maybe it's fine, don't know or really have an opinion either way. I do like the curve of the GSR dyno plot Greg posted (was jealous as mine is no where near as smooth) but that really doesn't matter as far as the process is concerned. Just peak, right?

[Z3_GoCar]

Since I'm leaving IT and the 2.8 behind, here's what I have for dyno plots, maybe it'll help put the car in ITS at its same weight....

The motor, it was professionally built in January 2001 for world challenge, stock aluminum block, head from a 1996 M3 3.0l S-50 including s-50 cams, M3 euro Supersprint long tube exhaust headers, S-50 OBDI intake manifold, titanium valve retainers, 11.5:1 CP pistons that are 0.003 oversize (that's an 84mm piston, not 84mm bore as came from the factory), Electromotive TECII ecu with 30lb/hr low-impeadance RC injectors, M3 lightweight oil pan and S-54 oil pump, M3 oil filter assembly with oil cooler fittings and S-54 oil cooler mounted under the oem radiator, since the ecu doesn't use a MAF it's been removed, and an aluminum single mass flywheel. The throttle body is stock, and had the original 325 flat-plat restrictor behind it. This is how it dyno'ed:


Now fast forward to making the motor as IT legal with everything that I knew about at the time. I removed the S-50 intake manifold, aftermarket fuel injectors, and aluminum flywheel, I added a MAF even though it's not connected to the ecu, purchased oe pink top 24lb/hr high impeadance bosch injectors, the correct OBDII intake manifold, and a dual mass flywheel. The result on the same dyno with the same tunner was:


So why won't it make power like the 2.5? The head's the same, intake cam phasing is the same, valve sizes are the same, cams are about the same, same piston bore, throttle body is the same. So what's different? The intake manifold is vastly different, smaller plennum, smaller runners that are round instead of oval shapped, smaller ports that can't be cut out to match the intake port vs intake ports that are manufactured to match the head ports, the rods are longer with a shorter pin height, so the compression ratio is 0.3 less (10.2:1 vs. 10.5:1). Simple answer, move the choke point into the intake manifold and no matter how you build it, it won't respond.

[JeffYoung]

Yes, just peak.

I think in ITS my car/Z cars/GSR/Miata/RX7s race really well. Zsolt's car has more mid than a good RX7, but I have a significant advantage over him in the early part of the rev range after a shift.

There is a 30 minute race vid, primarily between Zsolt and me, in the SEDiv forum here, where you can see this. Cars are very, very closely matched. I think Zsolt has a slight top end advantage but I'm stronger in the mid and up to 110-120 mph.

Good racing with that car (and driver! Zsolt is fun to race with).

What about 0 - 125 mph? Hey, maybe it's fine, don't know or really have an opinion either way. I do like the curve of the GSR dyno plot Greg posted (was jealous as mine is no where near as smooth) but that really doesn't matter as far as the process is concerned. Just peak, right?

[bamfp]

The average mph Zsolt does at Road A and VIR is 125-127. Gearing is what has helped his car down the straight.

[JeffYoung]

Have to check the T-mate but I think that is about the same for me on the backstretch at VIR. Zsolt could draft around me, and I could draft around him. He just seemed stronger at the back end of the straight, me at the front. No surprise there I guess.

I do have recent T-mate data for Roebling and it shows 128.

[Greg Amy]

Interesting to note that the Triumph TR-8 has become the performance benchmark against which everything else in Improved Touring S is to be compared. Good to know, though...

[JeffYoung]

It is for ITS Jeff, because it is the seat I sit in.....

Seriously, I understand you guys bailing on the ITS car. Ron and I were talking about this the other day, but at some point you get "ruleset burnout" and you just can't deal with some of the stupid/silly stiff inherent in the ruleset (and in inherent in any rule set) any more.

Plus you guys did a great job with the ST stuff. It may be the future of the SCCA.

I just don't buy the "GSR can't make power/can't compete in ITS" stuff. Fully developed (and you guys have to admit you didn't go full bore on the ITS car), I think it is one of the cars to have in ITS.

[Ron Earp]

I just don't buy the "GSR can't make power/can't compete in ITS" stuff. Fully developed (and you guys have to admit you didn't go full bore on the ITS car), I think it is one of the cars to have in ITS.

The GSR is competitive in ITS. Only Zsolt knows what sort of power GSR makes and if he wants to disclose that figure it's up to him. I've raced with him plenty of times though and he either had at least the same power I had out of my Sam Neave engine, which was 170 to 176 rwhp depending on temps. I suspect he had a tiny bit more.

I know that at VIR Zsolt and I were extremely close and I was able to observe numerous instances of the two of us leaving Oak Tree and him just able to get an advantage in the last 150 yards or so of the back straight. Aero or a few horsepower more? I dunno. But for sure his car is heavier than mine was. I've seen it run against a number of well driven ITS car types and it seems to hold its own.

If someone feels that GSR is competitve at 181 hp but it isn't at 172 hp then I think they're looking for an excuse to not run the car. The GSR as an overall package is competitive in ITS and the driver will determine the rest.

[Andy Bettencourt]

The E46 323 is an interesting bird. I have NEVER seen a dyno sheet but when one rolls our ITR S2000 up the esses at the Glen at the same weight, you would easily extrapolate 200whp. That puts that car about 150lbs light compared to the targets. I have no reason to believe the cars I am using as examples are illegal.

[JoshS]

The E46 323 is an interesting bird. I have NEVER seen a dyno sheet but when one rolls our ITR S2000 up the esses at the Glen at the same weight, you would easily extrapolate 200whp. That puts that car about 150lbs light compared to the targets. I have no reason to believe the cars I am using as examples are illegal.

These are not IT builds, and they include the E46 variants of the 323i, 325i, 328i, and 330i (323i and 328i are "M52tu", 325i and 330i are "M54") in all sorts of levels of tune, but ... based on my own car, which is the same as the 328i, and these dyno plots, I don't believe a legal 323i could get to over 200whp.

http://www.e46fanatics.com/forum/sho...d.php?t=768715

[Andy Bettencourt]

These are not IT builds, and they include the E46 variants of the 323i, 325i, 328i, and 330i (323i and 328i are "M52tu", 325i and 330i are "M54") in all sorts of levels of tune, but ... based on my own car, which is the same as the 328i, and these dyno plots, I don't believe a legal 323i could get to over 200whp.

http://www.e46fanatics.com/forum/sho...d.php?t=768715

I hear, as with the WC cars and some of the higher-end IT builds, that once you grab ahold of the VANOS with your progammable ECU, the power really comes.

[bamfp]

Before I left Sunbelt, we built an E46 engine with I think Motec,. It made very close to what Chet's E36 made.

[JoshS]

Before I left Sunbelt, we built an E46 engine with I think Motec,. It made very close to what Chet's E36 made.

Which engine?

[bamfp]

Honestly I don't remember. I am pretty sure it had dual vanos.

[JoshS]

Honestly I don't remember. I am pretty sure it had dual vanos.

They all have dual vanos. The 3.0 would have no problem making more horsepower than any E36. The others would take some good tuning, and I have my doubts about the 323i engine.

[chuck baader]

If I remember correctly, the ITS E36 motor was a 2.5 single vanos on the intake cam. CB