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what do you guys think? should i go with 4.10 gears? i currently have 3.90's. with UD pulleys, at least 310 hp...

 

As for your 4.10 question it would be a total waste of money going from 3.90 to 4.10 gears because you would only be turning the wheels 1/5 of a turn / engine revolution. It would take 5 engine revolutions just to make the wheels go around 1 complete time. You should have gone straight to 4.10's in the first place.

 

Now turning to your HP figures...

 

You don't have 310 HP until you dyno the car to show that....and you haven't according to another post you just made today. Your other post said your stock + tune "dyno" rendered 302 to the wheels. This is a VERY doubtful figure given just a tune to a stock Shelby.

 

As I stated in your other post - Considering that these engines tested at SAI and officially recertified to be 319 at the crank. Given the standard 12% or 15% powerloss going to the wheels the best these cars would do is:

 

at 12% loss = 280.72 RWHP (what most Mustang GT's with a CAI and 90mm MAF are making which is in essence a "stock" Shelby GT in regards to the intake setup.)

 

at 15% loss = 271.15 RWHP

 

Even the most aggressive tune on a stock Shelby GT will only net about 287 RWHP.

 

Something is going on with either the dyno your pull was done on OR the tuner is doing something wrong. Your figures are just way to high for just a tune of a stock motor. Even if your engine was what is known as a "freak" those figures are still way too high. Sorry to say man but something just isn't right with your figures and to me they are definitely unreliable.

 

I would go to a completely different dyno and see if you make 310 RWHP now that you have UD pullies. If you do that would at least verify the reliability of your first dyno as being valid.

 

I am not trying to be smart or "dis" you however I had three S197's of my own dynoed and have witnessed at least two dozen others dynoed and none of them ever reached 300 or more as "stock + tune)...and all did settle into a range between 275 and 287 RWHP.

 

It would benefit you not to be assuming figures (i.e. 310 HP) when you haven't dynoed it with the UD pullies you put on recently as your 310 wheel figure is based totally on what I am sure will turn out to be a bogus "stock + tune" dyno figure (i.e. 302 RWHP).

 

There are plenty of folks who have extensive knowledge and experience with dyno figures for an S197 GT and know when something isn't right. And your reported figures are absolutely suspect beyond a shadow of a doubt even when considering your engine as a possible "freak".

 

You really need to go to a different dyno and have the car redynoed...I am sure you will be quite surprised and are going to be disappointed as well.

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well as soon as i get it dynoed... i will post up the numbers... now you got me thinking... :( ... i definetly felt the power difference after the tune... but we'll see ..this guy that tuned it...hes one of the best... he reaches # that others cant with his tune... :happy feet:

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well as soon as i get it dynoed... i will post up the numbers... now you got me thinking... :( ... i definetly felt the power difference after the tune... but we'll see ..this guy that tuned it...hes one of the best... he reaches # that others cant with his tune... :happy feet:

 

Any tuner can get you big numbers and put you into the 300 range with these cars. That DOES NOT MEAN the tuner knows what he is doing. It could well mean that he is going to the dangerously extreme ends of the A/F ranges at the customer's expense (an eventual destroyed engine) in order to drum up more business because as rumor would have it "he's one of the best... he reaches # that others can't with his tune...".

 

And it would be very difficult to prove any liability on his part because you assumed the responsibility of anything that goes wrong by modding the car out of spec. And I am sure any tuner guy knows that he is going to be practically "free & clear". Again I would get another dyno BY A DIFFERENT DYNO PLACE AND DIFFERENT TUNER. And get the A/F ration figures done with the pull so you know what the hell is really going on.

 

This isn't all about HP...its about making the highest HP possible at the best balanced A/F ratio which is between 12.2 and 12.7 for these cars.

 

I'm going to add something...you said that you really felt the difference after the tune. That difference you "feel" is more than likely going to be the torque going on. My suspicion is that you will find that your A/F ratio (of the tune in question) will initially be somewhere between 14.2 and 14.7 for at least the first 3500 to 4000 RPMS and then he probably will have set the tune for the ECU to command more fuel in from 3500 RPM (or 4000 RPM) to the redline. This woulkd graph out as an initial A/F "spike and line" on the dyno sheet from 0 to 3500 (or 4000) RPM and then the A/F would "valley and line" somewhere in the low 13's the remainder of the pull till redline as more fuel is dumped in. The A/F ratio graph will probably not be smooth by any means.

 

If this is the case then this is a clear indication the tuner is a complete DICK despite his "reaching #'s that others can't" .......and I predict your engine will be trashed sometime within the next year or two.

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Wow, what a slam!

Maybe yes, maybe no, but in both posts, ShelbyKindaGuy is correct. Notes from my SGT dyno experience.

 

DYNO: bone stock, 20 Sep. 2007/Simpson Performance/DynoJet 240 in-ground.

275.55 RWHP/300.85 RWTQ

DYNO post shorty header install 12 May 2008/Simpson Performance/DynoJet 240 in-ground.

284.54 RWHP/306.80 RWTQ

DYNO post drive shaft install 2 July 2008/Simpson Performance/DynoJet 240 in-ground.

283.82 RWHP/307.22 RWTQ (dyno data invalid due to 100 % humidity)

 

Yeah, SKG could have said it another way, and not lost his message. Furthermore, I read 1218's other post on power gains to be speculation about his next mod, not a claim or brag of achivement. IMHO, in N/A trim, I believe the SGT's RWHP/RWTQ will top out around 325. That's not shabby power for 281 CID, but it is pushing everything to the edge.

 

what do you guys think? should i go with 4.10 gears? i currently have 3.90's. with UD pulleys, at least 310 hp...

As others have said, the difference between 3:90s and 4:10s is not enough to justify the expense. If you would like a few more ponies, consider a light shot of NOS?

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