TR6

Ok, I bought an hour today at a dyno to compare before and after results for a couple of mods. Ambiant temperature was in the low/mid 90's F and I run 93 octane pump fuel. Here are the results at the rear wheels. I don't think the absolute numbers themselves are as important as the delta in readings between the different variables I changed.

First comparison was between the stock chip, an autothority chip, and a Steve Wong chip (911chips.com). The only variable changed was the chip and all were run within the same one hour period strapped to the same dyno:

1) Stock chip, open airbox, cat bypass, secondary bypass - 210.5 hp , 201.6 Torque
2) Autothority chip, open airbox, cat bypass, secondary bypass - 205.6 hp , 208.1 torque
3) Steve Wong chip, open airbox, cat bypass, secondary bypass - 229.4 hp , 219.1 torque.

Observations:
The Steve Wong chip gained 18.9 horsepower over the stock OEM chip which is a roughly 9% gain. Torque gain was 17.5 or roughly 8.5% over stock.
The Autothority chip actually had less horsepower than the stock OEM chip, but it did have a little more torque than the stock chip.

Next interesting comparison was the Fabspeed open airbox vs. the stock airbox with the snorkel. Again, comparing only the one variable change (air box) within the same hour, same ambient air temperature (low/mid 90's F). Both stock airbox and fabspeed airbox ran with the same K&N air filter. Here are the results to hopefully shed some light on the airbox debates:

1) Stock chip, open airbox, cat bypass, secondary bypass - 210.5 hp , 201.6 Torque
2) Stock chip, stock airbox, cat bypass, secondary bypass - 208.8 hp , 203.1 torque.

Observations:
Well, technically, the open fabspeed air box added 1.7 hp but the stock airbox had slightly higher torque (1.5 torque difference). I would just about call it a wash and my guess is it could just be margin of error. I don't know that you could say that 1.7 hp is even a measurable difference. Quite honestly, if I had run the two runs without making any change at all to the airbox, I wonder if I might have gotten at least that margin of error anyway.

Questions:
1) Assuming 15% drive train loss, with the Steve Wong chip in place getting 229.4 horsepower at the rear wheels, my simple math equates to roughly 270 horsepower at the flywheel. Do I have that calculation right? Is 15% the right number for a C2 for drive train loss?
2) How much will outside air temperature affect the results? I asked the guy running the dyno if their system corrected for air temp and he said no, that it just reads lower when its hot. I wonder if I ran the same configuration on the same dyno when it was 40 degrees F. outside, for example, what it would show. Also, I was surprised that they didn't have much airflow going over the car. The fan they had in front of the car seemed inadequate in terms of flow. I'm not sure how one would simulate airflow of 130 mph on a dyno.

The next thing I want to play with are exhaust changes. For example, primary bypass vs secondary byass, Cat vs cat bypass, etc. The trouble is that dyno time isn't cheap and changing hot exhaust components is not as simple as changing chips and airboxes.

Here are the dyno plots for what they're worth. I don't really know how to interpret these so I'd be happy to have input. For example, I don't know why the gaps in the plots. Perhaps where he was shifting gears? And how does one interpret the air/fuel part of it?

First is the Stock chip, stock airbox
Second is the Stock Chip with open airbox
Third is the Autothority chip with open airbox
Fourth is the Steve Wong chip with open airbox

deep_uv

Excellent Greg. Great info. I guess the cheapest way to approach the exhaust comparisons would be to change your exhaust config then rent another hour and do the same tests as above. Then change exhaust and repeat again. Of course you throw in the ambient temp variable that way if you do it on another day.

What the hell, go for it. It's only money.

Steve

74carreraturbo

While you're at it can you get a sound wav of your exhaust setup?? Thats exactly what i'm planning and i still havent put the cat bypass on in fear of it being too loud!

deep_uv

Greg, One other thing. Based on our history of dicing it up on two different tracks, my horsepower must be off the friggin scale!

Steve

Cupcar#12

interesting..
i ran 251.7 whp (mid 80's degrees, Andial Chip, RS DME, Neg pressure oil breather, Stock cat, Cup Primary Bypass, Secondary muffler in place, 50/50 mix 100-92 octane, cut-Open Air box) and i am down about 20 on what cup/RS motor should do (WHP)

i will be doing the Fab speed cat bypass and installing my Secondary bypass for the next one

TR6

Or it could just be your superior driving skilz that allows you to keep up with me...

Ritter v4.0

Great thread. Thanks for sharing with us all.

Is Steve Wong's chip optimized for 93 vs the Authority for 91- could that explain the delta?
When you purchase from Steve do you give him basic useage details ( octane level, no cats, primary bypass) or is it one size fits all?

TR6

Yeah, Steve sent me a 93 octane chip that was optimized for exhaust bypass and cat bypass. I don't know what octane the Autothority chip is designed for, but I'm guessing a 91 octane chip might make a few hp less. I wouldn't have thought the difference would be as much as my results found though (24 hp difference) between Autothority and Wong. I had actually bought the Steve Wong chip to try to cure the periodic stalling problems I've had with the light weight flywheel, but unfortunately, it still stalls periodically on a hot day with the AC running. I've tried a couple of different chips to overcome that issue and still haven't found one that solves the problem completely. Jason is sending me a revised version of his chip to have another try to see if it can solve it.

As a side note, the Autothority chip raises the redline to about 7200 which I don't like. The Steve Wong chip keeps the stock redline. I like having that safety margin for engine longevity.

TR6

I wish I had recorded the sound of it on the dyno. It was a glorious sound as it ran steadily up to almost redline. I got a lot of compliments on it as a bunch of hotrodder and quarter mile guys gathered around to hear it run on the dyno.

Another side note: It was a truly butt clinching moment when it got a little bit loose on the dyno at close to redline and the car suddenly lurched and got crooked while guys were yelling "Whoa! Whoa!"

"We need to recheck those straps..."

Colin 90 C2

A few questions:
what type of dyno?
did you get the files?

A few comments:
afr scale needs to be zoomed in to get values.

the dropouts need to be filled in- should not be shifting gears as dyno run should be in 3rd or 4th gear from low rpm (2000) up to redline.

the best way to interpret results is to overlay the graphs. Peak hp and tq are great, but max area under the curve is more meaningful.

great job!

pu911rsr

Couple of observations, chassis dyno's are generally good for relative measurements only, just as you have used them. Yes your math is correct for drivetrain loss. It is not uncomman for Porsche's too make more HP than they advertise.
Phil

TR6

I know I sound ignorant here, but I don't know what kind of dyno it was. I'll have to call them and ask. Likewise, I didn't even think to ask for the files. This is my first time to go to a dyno and if/when I do it again, I'll be much more detailed in my preparations and the data I seek. In fact, if Steven C. hadn't been there with me this time, I wouldn't have even thought to ask the questions he was asking them. Like, "Be sure to aim that fan at the oil cooler intake..."

jjbunn

Wonderful. Real data! Thanks for posting.

Steven C.

Yes, we had a good time doing the runs even though there was very little air flow through the room and it was VERY hot in there. The big 5' fan they had would only run on low speed and Greg's hood shocks were shot so we didn't have a fan aimed at the engine(not sure they even had another fan anyway). With more air movement around the intake I am sure the car could do more but I think you got the big questions answered.

TR6

Steve, you'll be happy to know I replaced the hood shock yesterday evening. Stays up like a champ now.

I actually would like to look into finding a better dyno place next time. These guys didn't seem to appreciate the importance of good airflow.