Just this monday I had Garry Marsh tune my car after my SAFCII lost its settings somehow while the car was in storage for a year. He tuned it during March last year but this year I seemed to have some disappointing results.

We ran the car 9 times on the dyno making various adjustments but always with similar results. The car was running rich untuned so he leaned it out a bit. These were the basic numbers and best run results:

March 2004: 242 whp / 268 tq, temp = 88 deg F, 34% humidity (3 dyno runs) @ 15 lbs
April 2005: 225 whp / 253 tq, temp = 91 deg F, 15% humidy (9 dyno runs) @ 18 lbs

Everything has stayed the same with the car since last year. The only difference being that last year I dyno'd on 16" stock wheels and this year on 18" ADR Spades which are a few lbs heavier per wheel.

Garry thinks the humidity difference and hotter weather probably accounts for the 15 whp descrepancies. He's the expert so I put a lot of stock in his opinion but I'd like to know what is it about humidity that would make more humid weather help dyno numbers? Also at one point we upped the boost pressure to 20 lbs and the 1G bov held it but saw no increase in power vs 15 lbs so we lowered it to 18. Garry said without a fmic and larger injectors my T28 was probably at capacity. Keep in mind I'm on a fully race rebuilt a/t so I have some power loss vs a m/t with same mods.

While driving back home I remembered that also last year I ran on stock wheels vs the 18's on my car now and I figured that had to factor in somehow because it's quite a difference in size and weight. Garry wouldn't have remembered this and I did not have a chance to mention it to him yet. Could the new wheels have diminished my dyno numbers?

Come on, somebody has got to have some idea about this. Where are the tuning heads around here?

My guess is that higher humidity acts almost like a tiny Water Injection setup, helping to minimize knock. Do you have a pocketlogger so you know what kind of timing numbers you're getting?

Has the ATF been changed recently? Same tranny as last year's dyno runs?

Wheels could account for a small HP loss; I have no idea how much.

It could be the fact that you upped the boost on stock injectors and IC. Think about it, the stock ones suck as it is and then to place it on a dyno where absolutely no air is passing throught it with higher boost. Im sure that thing was completely heatsoaked.

I'm thinking heat soaked IC and heavier wheels did you in....not the weather.

doug said:

My guess is that higher humidity acts almost like a tiny Water Injection setup, helping to minimize knock. Do you have a pocketlogger so you know what kind of timing numbers you're getting?

Has the ATF been changed recently? Same tranny as last year's dyno runs?

Wheels could account for a small HP loss; I have no idea how much.

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Yeah Garry said that more humidity helps on the dyno but he wasn't sure exactly why. No I don't have a pocketlogger, I wish I did. I want to get a similar setup to what you have, dsmlink and all. I haven't changed the ATF but after I took it out of storage I had everything looked at and the ATF was good - level and color. Yes same tranny.

Garry also mentioned I should check my plugs. He said a 15 hp/tq discrepancy isn't really that much to worry about since it could be one of many issues, mostly environmental conditions.

RossY said:

It could be the fact that you upped the boost on stock injectors and IC. Think about it, the stock ones suck as it is and then to place it on a dyno where absolutely no air is passing throught it with higher boost. Im sure that thing was completely heatsoaked.

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Well the first run turned out 215 hp / 228 tq approximately. We cooled the car in between runs with external fan in the IC and a/c for 10 min or so each time. It took over 2 hours for the 9 runs. We didn't raise the boost until after 5 or 6 runs and being unable to turn up numbers as high as last year. Boost beyond 15 had minimal impact if any.

My SAFC settings right now are as follows:

Hi-throttle:

1000 ~ 5800 = 0
6400 = -1%
7000 = -2%
7600 = -3%

Lo-throttle:

1000 = 0
1600 = -3%
2800 ~ 7600 = -5%

Untuned I was basically running rich but with similar dyno numbers to after tuning. Adding any more fuel anywhere in the spectrum resulted in power loss. Leaning it out as shown in my settings resulted in the best dyno results. So seems to me that I just don't have enough cold air flow...I was able to add about 10% more fuel from those settings but lost power so the stock injectors seem to have a little bit more room in them. I do think that pathetically small smic is the limiting factor here.

Garry said I'm stuck where I am without a fmic and injectors.

heavier wheels would not of been the factor. heatsoak is definitely an issue especially on the stock sidemount and running that much boost. i would not worry about it. it gets hot in Garry's shop especially around the dyno. Garry's fan doesn't really do much on the dyno. he had a good one but every dyno day i host someone tends to kill a fan. i would invest ina front mount and water injection. i am definitely going with water injection as soon as i get my front mount and fuel upgrades. i am going to see what this little 14b can do. oh and did you check for boost leaks?
you need to come out to our meets when you are in town as well

Yes bigger heavier wheels and a bigger brake rotors can effect wheel hp out put. I have seen proof of this on Sports Car Revolution. Their Acura RSX showed a drop in in WHP after a wheel, tire and big brake upgrade.

Staytuned said:

Yes bigger heavier wheels and a bigger brake rotors can effect wheel hp out put. I have seen proof of this on Sports Car Revolution. Their Acura RSX showed a drop in in WHP after a wheel, tire and big brake upgrade.

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I thought as much because you figure the car must work harder on every rotation of the two wheels. My new wheels are approx 15% heavier than the stockers. That's a significant difference. I really need some lightweight volks or something.

vertGST said:

heavier wheels would not of been the factor. heatsoak is definitely an issue especially on the stock sidemount and running that much boost. i would not worry about it. it gets hot in Garry's shop especially around the dyno. Garry's fan doesn't really do much on the dyno. he had a good one but every dyno day i host someone tends to kill a fan. i would invest ina front mount and water injection. i am definitely going with water injection as soon as i get my front mount and fuel upgrades. i am going to see what this little 14b can do. oh and did you check for boost leaks?
you need to come out to our meets when you are in town as well

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My uncrushed 1g bov held 20 without leaking although it did not make even 1 hp of difference vs 15 ~ 18. I considered a smic, either dejon tools or supra, but Garry said it wasn't even worth it...just go fmic. If I do that I might as well swap out the front end to a oem 2Gb since the smiley is so cluttered for a front mount, or just get a buddy club 2 front end. But before any of this, I have to go find myself a job again.

Considering street performance, the tuning does seem to have improved my performance. The pulls seem to be a bit harder higher in the rpm range. I guess in the end that's all that counts.

I definately want to make one of the meets if I'm down there when you all have one.

Going to big wheels like 18s can hurt HP output at the wheels. I have seen it happen on cars before.

If he was using SAE correction, it should take most of the humidity and temperature differences into account and give very close numbers from one weather condition to another.

High humidity does not act like water injection, it just lowers the amount of air that can get into the motor because it is taking up space, which ends up lowering power output.

garry is a fan of the top to bottom front mounts and he had quite a few cars at his shop with them . its fits the smiley bumper fine. on the other hand you can get a 2gb bumper for $70 aftermarket. my car really does not make any more power over 17-18 psi on the stock sidemount the numerous times i was on teh dyno. i can't complain with mmy numbers though. i am pretty sure you car has a walbro 190 in it but i can not recall if ricardo had switched out the injectors or not.

Hello !

Well, I was the previous owner of the car in question as some might not know.

When I dynoed the car last time I didn't have AFC and my a/f ratio was below 10.0. My boost was at 15 psi, it still put down 230whp, which is more than what you have now. Very weird. My opinion :

1. Considering the AFC adjustments were very small, seems like you are not running that rich after all, it seems like you might be running too much boost and the ECU is retarding your engine timing, thus causing you to loose some power. Remember, the fuel pump is Walbro 255 High Pressure, but the injectors are stock. The ECU makes its calculations based on injector size...

2. Larger and Heavier wheels are for sure stealing you some power.

3. Check your boost gauge for boost level at high rpms. Horsepower is directly related to your high rpm power, torque can be provided at low rpm when turbine is reaching its peak but it might drop too much if your boost does too. It would be useful to get better conclusions by looking at your dyno chart. But check to see how much your boost is at the 5500-7000 rpm range, if it drops to 12 or below this might be why you are loosing so much power. Check for boost leaks (intake leak tester at vfaq.com) and install an electronic boost controller to get proper boost at high rpms, this will ensure you more power. Boost spikes and peaks will affect your power and confuse your ecu.

(if you reach 20psi in a short peak at 4000rpms, the ecu will see this much airflow and probably retard your engine timing [get larger injectors], but then your boost drops to 15 and then might even drop to 12 at high rpms[get electronic boost controller], by then your engine timing is definitively not as optimal for power as it could be)

Thanks for the feedback all. Everything keeps coming back to the injectors and intercooler so looks like I'll have to upgrade those first thing in order to start making any progress here. If I do those I'll also upgrade the turbo at the same time. Might as well do it right. I'll change the front end and hood as well just to get more air flow.