Engine decisions

[Factionite]

So I've been looking around for various engines for quite a while and am having a difficult time figuring out what engine would be best for my purpose. There are a lot of new Vett's and some Hellcats around this area and I want it to be able to beat them in a race. Which means 0-60 is 3 secs, 1/4 in under 11, and preferably about 900 hp with reliability coming in last. I've been reading a lot of people complaining about the thickness of the cylinders in the ls7 and lsx models and it has me worried about its reliability, to that extent most people suggest that you don't put a supercharger on the ls7 or lsx. So then I though I will just go with like the ls3 and get a supercharger but I don't think its going to make 900 horsepower as easily as the ls7 and once I get it to that point it will be equally unreliable. Can someone chime in what would be the most reliable way to build 900+ hp? I don't need specifics, but if someone can say XX engine plus YY mod and ZZ mod would get close to that number and could still rest easy after the 100k mileage mark that would great.

[mlkwd1]

Of course this is a personal choice and often has nothing to do with what is best or practical. You will get an unlimited amount of opinions to help you spend your money. For consideration, I have a LS3 crate motor with a more aggressive cam. The car weight 2500# wet so the effect of a high horsepower motor is more dramatic than it is in a 5500# muscle car. Whatever the horse power of this motor is, I had to change the rear tires to Toyo Proxes R888 335s because I could not hook the car up in a straight line with the 315 Yokohama Avons. You could spin them at 100MPH shift into fourth gear. Not sure what the zero to 60 is but is far sub 3.0. You have to consider the transmission you plan to run. The Porsche G50 transmission is not made for much over 500 HP. You can do a LS3 crate motor for 8K total brand new and a couple hundred for a upgraded cam. Very little work to get them over 500HP. When I need to change the motor, it will be the 525 HP LS3 crate motor for about 10K. I can't picture being able to use much more horsepower than a tuned LS3 525. What you need to choose is what works for you.

[eseethal]

The LS-7 in the GTM is a good (but expensive) choice - even stock it is scary fast in a GTM! As written bei Factionite the problem is to put the power down. My LS-7 sometimes spins the 335 rear tires in 4th gear! I cannot imagine how traction would be in a supercharged 900hp GTM!

[Factionite]

Thats great to hear about spinning the tires in 4th gear! Thats the kind of power I'm after . Thats something I will have to consider when I build it. I'm actually surprised to hear that it could do that because of the way the engine sits. Maybe a wing will give me the extra downforce to prevent that, or i can modify the suspension in way to prevent it. If anyone else has more to add I'd be happy to get some more feed back.

[Edgeman]

Traction control would be the first thing I would buy. I had the LS3 and it had more than enough power and it would spin the tires off (Michelin PS2). So it don't matter what motor you put In, get traction control.

[David Hodgkins]

A quick word of caution; We don't talk about street racing here so I'm assuming when you say you want to beat them in a race you mean the track...

[Kempo]

Don't want to be "THAT" guy who tells you what you need or don't need so please don't take it that way. You don't need 900WHP to beat 99% of hellcats and vettes out there. Take into account that the GTM only weights 2500-2600#. With just 550WHP a GTM can easily run in the high to mid 10s if you manage to make it hook up. I managed to get 550WHP on my car with an N/A LS3 stroked to 418ci. Do the power to weight math on it and compare it to the cars you plan on racing. That will give you an idea of where you stand. My car for example weights 2660# divided by 550WHP= 4.83 P/W ratio. A 4000# car would need 800+WHP to match that on a GTM.

If you still feel you need more just install a stock LS3 and a turbo setup (much easier than the S/C route IMO) and you can run 800+whp all day long with a stock LS engine. That will be insanely fast. You will need a good trans-axle for that.

This will give you an idea of how reliable the stock LS is under boost.

http://www.performancetrucks.net/for...-going-485734/

[Roger Reid]

Traction control would be the first thing I would buy. I had the LS3 and it had more than enough power and it would spin the tires off (Michelin PS2). So it don't matter what motor you put In, get traction control.

I put the Race Logic traction control in my GTM. It is almost finished (at Shanes) so I have not tested it yet. My reasons for the TC was for auto crossing. The GTM is a mid engine layout. Once you start to spin out it is difficult to "catch". Once you spin beyond a certain point, you can't recover, you've lost control and that mega thousand dollar paint job is toast.

[The Stig]

Good for You Roger!

I've heard that Race Logic no longer offers the traction control unit going forward. That's a shame.

I'm not sure of other companies that offer a similar product as a stand-alone unit. Motec and a hand full of other ECU makers have it built into their systems and can be programmed. But they charge quite a bit for it.

Looking forward to seeing your car when it's done.

Mike

[Factionite]

Thanks for all the replies, I was looking into traction control already but I wasn't sure at which point I was going to need it. Sounds like it will be something to strongly consider for anything going north of 600 HP. That's great advice! I guess i sort of expected it to handle like an AWD vehicle but maybe not the case. Also has anyone done anything with paddle shifters on the steering wheel or installed automatic transmissions? If so I'd like to hear what their experience was with the install and the result.

[carbon fiber]

The paddle shifters are a no no on a standard h-pattern trans. It's been tried with catastrophic results. There was one car that was stretched to use a vette transaxle. (looked like garbage and probably ruined the handling) The best bet is a graziano transaxle from the lambo Gallardo/Audi r8. You'll need a custom adapter for the ls engine and a strong clutch setup. (see Dhanish thread on the other forum) You'll also have to have custom axles made for the extra power. (check out My Race Shop - Crash sells them in 300m) You're looking at around 15k for all these upgades behind the engine. There are sereral guys who's put crazy power in a GTM but it's not cheap and it's hard to put to the ground. Even with massive back tires and mid-engine design you'll break the tires loose because the car is so light. There's one with 1100hp but he could only run 10.5 1/4 mile times because of wheelspin. (500hp ls7 runs 11 flat) That's a lot of work and money for half a second in the 1/4 mile. Try finding someone with a finished GTM and get a ride to see how the car accelerates with a n/a engine. If you want the fastest 1/4 mile times the GTM is probably not what you're looking for. JMHO.

[Roger Reid]

...The best bet is a graziano transaxle from the lambo Gallardo/Audi r8...

I have an R8 with the S Tronic transaxle. It is fantastic. I would love to see one come up for sale at a reasonable price. Trying to adapt the TCU would be a nightmare.

[carbon fiber]

Just for clarification I meant the manual Graziano. I'm pretty sure no one has done the Graziano S tronic or Porsche tiptronic because of the complicated electronics. The manual Graziano is available for 10k new.

[Factionite]

That's a good point about the increased horse power an extra 600 hp isn't worth .5 secs off the clock in 1/4 mile. However I watched some videos about aerodynamics am wondering if some body mods might be able to increase the down force enough to make a difference. I saw some rear wheel drive corvettes do 7's so I was thinking that the gtm would be able to beet that but they also weigh about 1000 lbs more than the gtm and have more down force. However too much down force means fighting more air and will require more horsepower to reach higher speeds due to increased resistance. I really wish I knew someone from Colorado who had a gtm.

[carbon fiber]

The aero isn't going to help traction at lower speeds much. (under 100mph) I think you'd be impressed with a n/a GTM. I was going to do an over the top high-hp build but after doing some research it doesn't seem worth it to me now. I'm focusing on the suspension and aero and less on top speed. Most of the time it'll be on the street and plenty fast. The GTM will do 0-60 in 3.2secs. with 420 crank/hp. The best part about the GTM to me is having a cheap reliable engine that will still be f'n fast. As far as running 7's (1/4 mile?) a car has to be set up just for straight line acceleration for that, usually at the expense of handling/driveability. Call FFR and see if they'll give you a ride in their demo car. It would be worth the flight out there.