H22toF20

It took some searching but here's the AP1 OEM exhaust vs HKS 75mm. Keep in mind this is with the OEM computer. I've saw similar gains on an H22 that already had a 2.5" and a tune.. The guy made just as much power again with tuning.
https://www.s2ki.com/forums/index.php?showtopic=813260

Their was also a dyno somewhere on here of the HKS 75mm vs a skunk2(2.5" I think) single. The HKS made more power.

Gernby

I don't want to criticize UMS Tuning, but I sure wish they would have provided before / after AFR plots. I also don't really put much value in tests using the stock tune, since I' don't think ANYONE who cares about performance should spend $1 on bolt-ons before they have a "decent" tuning solution.

I'm not saying that a 70mm exhaust is just likt this, but tests like this one remind me of the FF header. The FF Header made great gains on a stock S2000, but as soon as they started testing it against the stock header with a tune, the gains diminished.

dan_uk

mine baselined 210 on the Mase Engineering dyno with the 70mm exhaust and AEM CAI on the stock ECU. Ended up about 222HP peak and a load of midrange when tuned with the aem ECU.

Gernby

I had to read this post and mine a couple times to figure out the significance of your post. If you said that your car was dyno tuned by Mase with just an AEM CAI, then baselined, then you installed the 70mm exhaust, and Mase tuned it again, then that would be a conclusive test. However, when people do a baseline of an untuned car, then tune it and dyno it again, that's really showing what the tune did, not what the parts did.

My example about the FF header was to show that sometimes parts ONLY make gains on an untuned vehicle, but if you do a tune on the car with the stock part AND with then another tune for the aftermarket part, those gains sometimes go away, which was the case for the FF Header (according to the FF header thread). Again, I'm not saying that's necessarily the case with a 70mm exhuast.

On an note unrelated to your post ... One thing I think I should have mentioned above is that I'm not against 70mm exhausts, and I have no reason to twist the results to "devalue" 70 mm exhausts, especially since I'm not being compensated in any way for these tests, and have NO WAY to ever gain anything from them. I've spent hundreds of hours, and logged over 1K miles doing the testing, at very low MPG's I might add. It's costing me a lot, but I'm doing it because I want to know what really does what. So far, my PWJDM intake and 60mm test pipe have made MUCH, MUCH bigger gains than anything else. The 2 exhausts have been the only bolt-ons I've tested that literally showed NO CHANGE.

chef-j

Why not throw this on real dyno? If you want to do it again, i let you borrow my Ti-c single.

dan_uk

What I mean is it made gains tuned and untuned.
Heres the history of all my dynos in date order:

Stock 191 RWHP dynojet SAE
Megan Testpipe 194 RWHP dynojet SAE
Megan Testpipe + leaned VAFC 197 RWHP dynojet SAE
Stock cat + leaned VAFC 195 RWHP dynojet SAE
70mm exhaust + 70mm TP 200 RWHP dynojet SAE

70mm exhaust + 70mm TP+CAI 210 RWHP dyno dynamics
70mm exhaust + 70mm TP+CAI + AEM ECU 222 RWHP dyno dynamics

dan_uk

you think if I put the stock exhaust back on and got it re-tuned it'd make more power?

chef-j

Dan_UK,

what 70mm exhaust you have?

dan_uk

T1R-EM single

Gernby

I wasn't going to answer this question here, since I want to keep the arguments about the soft dyno over in its own thread. However, I think this question is relevant enough to this thread to go ahead and aswer it.

First, the soft dyno is just as "real" as any dyno. It's just not a "conventional" dyno that people are used to talking about. My education is in engineering, and so was my career until about 4 years ago when I went over in to software development full time. The science behind a DynoJet is pretty basic, and is easy to duplicate using a datalog with high sample rate. Basically, a DynoJet measures output in the same way that my soft dyno does.

Now to answer your question. The reasons why I didn't do the testing on a conventional dyno are:
1) I don't own a conventional dyno, and would NEVER conduct tests like this if they cost me $100 / hour
2) Conventional dynos don't account for changes in weight
2) Conventional dynos don't account for heat soak or IAT's
3) Conventional dynos don't account for air flowing into the front of the car at 80 MPH
4) It's impossible to use a conventional dyno to test a car that is TRULY at normal operating temp, as if it had just come off the highway after cruising at 60 MPH for 30 minutes.

When I do tests like these, I always have the same contents with a full tank of gas. I do it with the top and windows up, and with the A/C off. I use the same exact patch of road (very smooth and flat), and only do it on days with insignificant wind, with dry roads. I also drive the car at highway speeds for several miles, and do several WOT sprints to get all the fluids up to temp (engine / tranny / diff oils). Then I do 4 WOT pulls in succession, and use the 3 most similar plots to creae the "official" plot, which is an average of the 3. By doing these things, I consistently get repeatable plots that show far less variance than any DynoJet I've used, even if there's months between the tests.

I did my usual soft dyno testing procedure immediately after leaving the S2000 club dyno day last month. I used the results from the dynojet to "dial in" the correction factors that the soft dyno uses to compensate for gearing, aerodynamic drag, and SAE correction factors. Here are those 3 pulls.



Then I saved the average of those 3 pulls as my "official" soft dyno results to be used as a comparison to the club dyno day results.



Then I used the WinPep software to export the actual DynoJet data to Excel, so that I could put them both on the same graph. Red is the actual DynoJet plot, and Green is the soft dyno plot. Pretty similar if you ask me.