ET for various Downpipes?

[dthrock]

Ok Ive searched the board and havent come up with this info. What I want to know is at what point is a 3" dp needed, 3.5" dp etc.

Im asking because there is presently a 2.75" DP on my car (long story how it got there). With the mods in my sig would it do me any good to go to a 3" dp? I dont plan on going to any larger turbo or injectors.

Also at what point do you gain anything from going to a larger crossover?

Dave

 

[John Craig]

Dave,

Is your DP (2.75") attached to a stock elbow?

John

 

[dthrock]

Ported stock elbow yes.

 

[QuickWrench]

Check my signature for some stock downpipe numbers.

Personally, I've never seen a 3" downpipe benefit much at all until you're WELL into the 11's. Considering that you've got a 2 3/4" unit on there, I'd use those dollars toward some Metallica tickets until your tuning's under full control.

 

[turbonatr]

I'd worry more about your tune than the DP. You have enough mods to put you WELL in the 11s as it is. I'd take the money you would spend on a 3" DP and definately get rid of the Flowmasters. They are not very turbo friendly. Get yourself a straight-through muffler like a Dynomax Ultra-Flo or similar. Flows are of baffled design and are restrictive. There is a dyno test comparing Flows with Ultra-Flos on www.turbomustangs.com in the "project car" section. The result was a gain of nearly 30rwhp and quicker spool up time when the Flows were ditched in favor of the Ultra-Flos.

 

[John Craig]

Dave,

As long as your stock elbow was properly modified for the PT53
turbo, I think you should listen to QuickWrench and turbonatr.

John

 

[dthrock]

I dont have flowmasters on the GN, those are on the stock TTA. I have an ATR 3" system on there. I know I have an 11 sec car, The numbers on there are in complete street trim, pull into the pits, empty the trunk and let some pressure out of the ET Streets. Also the track here is very bad. Even the slicks spin here. Add to that the 3700 ft elevation and you get a nice 12.50 ET in street trim. Ive only been to the track twice this year and both times Ive averaged dropping .35 off my time. (started from last years times of 13.20) The tune is getting there. A couple more trips should see some 11.90s at least. Just takes time.

Dave

 

[turbonatr]

Tuning should be done by watching your MPH, not your e.t. Your trap speed is what tells you how much power your car is making. Tuning by e.t. isn't really recomended since there are too many variables, like tire spin. Your MPH should remain very close to the same, though. For example, my first pass on drag radials netted me a 13.50 at 123mph. Tons of tire spin, but my MPH was very close to what I normally run with good traction. As I learned what the car wanted as far as launch RPM and boost pressure I was able to coax the car to 11.20s at around the same MPH.

Your 108mph trap speed indicates the car really isn't too far off e.t. wise. The car should be right around 12.20 to 12.40ish. Now, if your trap speed was in the 112mph range, i'd say you definately have a high 11 second ride with good traction. Work on getting your trap speed to come up. That will ensure you are making more power and starting to optimize your tune.

BTW, stick with the stock crossover until you well in the 11s or even 10s. I've gone high 10s with the stock headers and crossover.

 

[dthrock]

Sorry left that part out, I also gained 3mph from 106 to 109. My fastest ET wasnt my fastest mph. That was 13.0 at 109 with a lot of spin. I have a low timing chip in and hopefully will be getting a little hotter one from turbotweak once he gets moved. I think that will bump me up some as well.

Dave

 

[turbonatr]

108-109 still puts you right around the low-mid 12s. How much boost are you running?

 

[dthrock]

Originally posted by turbonatr
108-109 still puts you right around the low-mid 12s. How much boost are you running?

About 22-23#, I think thats about all I can get out of it. I have more turns on the rod, but then I cant get it back on. Seems like the spring is compressed as far as it will go.

Dave