MichaelTT

sorry we missed the chat last night...02BENME, Ellen and I had dinner, watched part of her DV Palau diving tape (nicely done) and then crashed...beat after the days activities. Concerning dyno testing...I have the charts that you all are seeking and will scan in...SCTT if you want to do a combined chart that will be very interesting (02BNME had volunteered to do but he is now on his way to Boston and then back to Reston and can not do for about a week).
I have looked over the readouts from the TTsdyno runs...a few observations on four of the cars:

-02BNME's 225TTR confirmed what he said he had been feeling for quite a while in that the engine has a surgey/power spiky (that is a tech term ;-) feel and the read out verified that...conclusion is a faulty boost control solenoid...and since we (that is Bill and I) are not experts on this device he is taking to Audi dealer for analysis.

-Many of the chips tend to run lean air/fuel mix ratios...15+ to almost 17 to 1 whereas 14s to 1 is optimal. All the ECUs (including OEM) ran rich at the higher rpm and thus the sudden power drop. Anything above 6K rpm you are loosing torque and HP. Cliff and I were discussing and he theorized that reason for the rich was knock control at the higher rpms...I then added that this rich fuel-air mix could be the result of the knock sensors and the corresponding adjusts of the ECU reacting to the input from those devices.
-In my opinion I do not see a problem with variations of output for two 'identically' set up cars...this could be a result of engine manufacturing differences (Audi states that the 225 engines output MINIMUM as advertised [225 hp and 207 lbs torque and if higher fine), versions of the ECU software (update variations that is) and yes some +/- variations of the dyno itself. Looking at the two MTM chipped and non resonated Forge Miltek exhaust 225TTs (I am leaving out 02BNME's car for two reasons...apparent boost solenoid problem and he has a UUC exhaust...no that is not bad just a variation not applicable to the analysis below)
(I am using a 120% conversion factor (maybe 117% is better?...select whatever you feel is appropriate and readings are SAE)
Dave W 225TTR 214 hp (wheel) 257 hp (crank)
257 T (wheel) 308 T (crank)*
AMULETT 209 hp (wheel) 251 hp (crank)
254 T (wheel) 305 T (crank)*
*if you use the 117% factor then T would be 301 lbs and 297 lbs respectively
% deviation between the two cars is ~1% for Torque and 2+% for hp
Now what does that tell you...nothing other than the PEAK output and for me that the results are well within acceptable range for variation between 'two identically set up cars'.
There are so many different ways to look at the readouts, but one that interested me was at WHAT RPM did you have the best readings and again Dave's TT and AMULETT are close:
Dave 225TTR max T at 5100 rpm
max HP at 3700 rpm
AMULETT max T at 5000 rpm
max HP at 3400 rpm

Both cars were running air/fuel ratios on the rich side starting at 5500 rpm and thus both were seeing the power drop at the same time.
Now looking at Aaron's total OEM 225TT (I am noting both runs):
Run 1 229 HP 223 lbs torque
Run 2 232 HP 226 lbs torque
At 117%factor run 2 would be 227 hp and 221 torque

Max HP was in the 3800 to 4200 (depending on which run) rpm range and max toque was ~5600 rpm (both runs).
Do what you may with these numbers, but I feel the results are valid and yes there were some surprises in some of the cars tested. After posting the charts you all can have a go at translating.
BTW I greatly enjoyed the day and meeting everyone (some new TTers to me) and seeing friends again. Beautiful sunny day, low 70s temp, under a high pressure (that is for you analyzing tech types when translating the charts)...will post a few pics and several videos of the runs. For now I hope I have help in explaining our Dyno Day and runs.

Here is JPCliff's car on the dyno and strapped down...
<img src="http://pictureposter.audiworld.com/4128/cliff_tt_on_dyno.jpg">

And AMULETT on the dyno...in front of car is a large cooling fan, to left the dyno computer and wheels resting on the 4 dyno rollers (basically a 4 wheel dyno is really two dynos linked together..in simple terms)
<img src="http://pictureposter.audiworld.com/4128/amulett_on_dyno.jpg">

Thanks Dan (MachV) and Chris for setting up...now off to coffee.

225TTR

2. Each car had multiple (mostly consistent) runs.

undrway

I was the sole 180 FRONTRAC at the event. I wasn't scheduled, just showed up to visit with some friends, and by luck or fate an opening appeared in the schedule, so I dyno'd my TTR. I am very pleased with my results. I ended up with HP: 161, T: 169 ft-lbs @ 3250. Now, I don't know what factor to apply to get numbers at the engine --- I believe the only *true* way would be to measure both at the engine and at the wheel on my car and calculate a car-specific value, but lacking the facilities and motivation to do that I opted to do my analysis at 115%, which I believe is the number Audi has put out. Still respectable at HP: 185 and T: 194 ft-lbs -- well over stock published numbers of 180 & 173 ft-lbs. I will be *very interested* to re-measure my car once I chip....perhaps some chip folks would also be interested in comparing these stock numbers with post-chip numbers in my car....who knows? Anyways, I will definitely want to re-dyno on the same machine, prefeably on a similar temp day.

Now my questions:

1. Can my measured hp even be compared to the published value? I ask this, I guess, because I am unsure of exactly what bhp is --i.e. "brake" refers to what? I will have to do a search.

2. What effect will an aftermarket exhaust have? I understand that the idea is less restrictive flow of exhaust gases; however, isn't there a certain amount of back-pressure created by the stock exhaust that is assumed in the design engine? Will decreasing this back-pressure actually cause less efficient combustion and/or less power created? I'm really not sure where this idea came from, but if it can't be substantiated, I need to get it out of my head....

It was very nice to see familiar faces again, and to meet new friends! I look forward to seeing you all again nex week!

JazziTT

hugh199@attglobal.net

Thanks..

Rave'nGTi

14:1 is only optimal on a naturally aspirated vehicle... that is WAY lean on a boosted car.

on a boosted car you want a nice 12.5 A/F ratio... no leaner than 13:1.... leaner than that it gets dangerous... even in really low boost situations (ie.. 6psi of boost)

I agree that the top end on these chipped cars needs leaned out alot... 10:1 is WAY fat... and that will kill alot of power... but you dont want to go any leaner than 12.5:1. You need to see a nice even A/F ratio... about 14:1 when your not under boost...and then fattening up to 12.5 as boost kicks in and rises.

PanTTher

It looks as though everyone had a great time doing this. It would be fun to take a look at the plots so please e-mail away. My account doesn't have a size restriction so large files are no problem. I'd like to do a relative comparison between cars and not worry much about absolute numbers. I'm curious about the power delivery at the wheels as a function of rpm. I won't have time to look at the plots today but I can sure start tomorrow night when I get back from work.

MichaelTT

Great! Scanner is back on line thanks to 02BNME and Ellen...

MichaelTT

should contact Audi and explain their errors....

PanTTher

:-)

smallTTs

You probably got the most accurate numbers due FWD. The second dyno adds to the variables.

FWD is slightly more driveline efficient than AWD. Remember that haldex is working on the dyno.

You are ABSOLUTELY correct that the most accurate way to compare engine flywheel hp & T (which is what factory uses) with hp & T at the wheels (chassis dyno measurements) is to run the same engine both ways. However, if your 180 is stock including exhaust, etc. I'd use the 180/161 =112% correction for your case. The torque is a little high, but remember that the computer manages that and it may have a little problem holding it down.

Both flywheel and chassis dyno measurements are 'brake' measurements because the power is being absorbed just like the brakes on you wheels absorb the energy the moving vehicle has.

Aftermarket cat-back exhaust should raise both hp & T.

In spite of what you may hear, less back pressure in the exhaust system will virtually always increase hp & T. The fuel and spark may need to change, but the computer easily adapts to this. Remember it measures the air going into the engine (MAF) and adjusts fuel as required (within the 3-7% increase the exhaust will give). Freer exhaust = more turbo speed = more air from compressor.

The 'urban legend' of necessary back pressure is just that. Yes, delete it from your head.
BTW, it is possible to screw up the exhaust with too-large or mismatched components and lose power, but if you stick to cat-back from a reputable (and tested) manufacturer you'll be fine.

You have a good, logical, no BS feel for this, Greg. You goin' to FW?

My $.02