Finally raced my cousins Trans Am

crazykid2056 said:

I've had my '05 GT for about a month and only have Flowmasters as of right now. Whne I get home form school this summer, plan on modding further.

Well, my cousins '99 Trans Am is auto, free mod's and exhaust. We first raced from a 5mph roll and he walked me pretty bad. I guess he had a car length by the time I shifted to second.

Then on the highway, we nailed it around 80mph. The LS1 just left me. (WTF)? I figured my car should be in the mid 13's!

Anyways, he's cool and going to help me mod the Stang this summer. It sucks though that his Trans Am has 98,000.00 miles, all dented up and stock but still hauls like that.

Sucks

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Its pretty simple really, both cars weigh about the same but the GT has 300bhp whereas ANY LS1 Fbody has about 345bhp (regardless of what GM quoted, as they where underatted).

So with more power they should be quicker.

An 03/4 Cobra has 390bhp (possibly underatted, but unlikly as they just don't dyno enough rwhp in all reality), but they do weigh a little bit more.

But they still have the HP advantage so it should win.

s/c Cobra -> LS1 Fbody -> 05 GT -> sn95 GT

Apart from that its all down to the gears, some of the auto LS1's have very tall gears, these are the ones that can be beaten more easily, but a well driven M6 (totally stock including exhaust and air box) has the potential (not that everyone is a good enough driver) to see high 12 second ET's and trap 107-8mph where as a stock 05 GT is more likely a mid (13.6+) car trapping 98-101mph.

Also remeber the Fbody's have quite slippery aerodynamics too and most of them will top 160+mph.

Get a few mods done and race from a dig at the track and it may well be a different story.

The Answer lies here my friend: http://www.procharger.com/2005_mustang.shtml

svtguy said:

390hp translates into about 335rwhp, you could pull out a spark plug & most 03/04 Cobra would still put down that number stock.

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that all depends how you work it out. Any form of calculation/working out is never going to be 100% accurate either, only a an educated guess as there are far too many variables.


The 15% rule:
390 /.85 = 331.5bhp but this would then be working on the bases of a SAE Net figure rated at the wheels, well as near as damn it as SAE Net has to be rated at the flywheel, but it would be using the same rating scale.

Rolling road dyno's (Mustang/dynojet) do not usually conform to this standard of rating so could easily dyno another 20+rwhp higher, but it would just be a different rating NOT a higher output from the engine. Same as $1 US dollar has a different value to $1 Australian dollar yet they are both dollars. So chances are if a car dyno'd around the 350rwhp mark by the time it has been corrected to SAE Net standards the figure would be around the 330-335rwhp mark.

However, some engine builders claim that most Mustangs usually loose 30-40hp thru the drivetrain regardless of engine output (except in some extreme examples) so 390bhp - 30 or 40hp would put them dynoing around 350-360rwhp mark on a rolling road dyno.

The % theory is very flawed, as different cars (makes, models even the same car with different wheels or milages on the clock (higher milage = more wear on bearings/bushing, etc.)) will all loose a different amount thru the drive train.

IMO the variable % rate is more accurate, basically it follows the logic of the higher the engine out the lower the % loss but hp loss still increases, for example (these are not real figures and are only used for illustration purposes):

250bhp flywheel, looses 15% (250 / .85 = 212.5rwhp)
A loss of 37.5HP

500bhp flywheel, looses only 10% thru drivetrain (500 / .90 = 450rwhp)
A loss of 50HP


The Cobra's are one hell of a car and rank high on my list in my fantasy garage, but if they ALL really produced over 400BHP SAE Net I'm sure Ford would have advertised the fact, for two reasons:

1. The Cobra is Fords premier performance model in the US (forget the GT, but that didn't exist then and is a totally different league), so there was no higher end car to steal sales away from in the Ford group, unlike GM they deliberatly underated the Fbody's so as not to over shadow the Corvette with the same engine, it was of course a lot cheaper to purly'Advertise' a lower BHP than actually go to the expense of detuning the units or building specific spec units just for the Fbody. Very clever in all reality.

2. The Corvette Z06 had 405BHP SAE Net, and although slightly more expensive could well be considered as an alternative to the Cobra, so it would have been beneficial for Ford to advertise the highest BHP but they didn't they advertised less than the Vette which again would indicate that the engine did only produce 390BHP SAE Net.


This all adds up that dyno numbers and even manufacutre claims can not and should not be taken literally as there will always be a variance in too many areas.

Another good example would be three 400bhp cars, one from the US one from the UK and one from Germany

The UK car is likely to be rated on the DIN system and 400BHP DIN is slightly more powerful than 400bhp SAE Net (if memory serves)

In Germany it would be 400PS (PS meaing Horse Power) but this is metric not imperial HP so 400PS would actually equal less than 400bhp SAE Net.

Gets very confusing doesn't it