V8 MKIV Supra from Saint Lucia.KHAOS!
 

Link from the original forum.
http://lucianriders.com/forum/viewtopic.php?f=29&t=559
Feel free to join the forum as well. 1.
Enjoy!

Thank you for the link.



As you might have guessed, you've posted on a forum full of 'Supra biggots' (speaking primarily for myself, if not more). I hope you don't mind if I provide some honest feedback from myself personally on that v8 Supra project documented on the other forum:

1. Several Mkiv Supras are in the low 8s (full weight!), and even a few in the 7s using the mighty inline-six 2jz-gte.
2. The 2jz-gte's in these low 8s Mkiv Supras typically put out 1400rwhp+
3. I absolutely do not understand why there's any appeal at all to "600hp without the help of boost" :confused: Exactly what does "without the help of boost" buy you, other than the excess weight and poor fuel efficiency of a much bigger, inherently unbalanced v8 block to lug around?
4. With only 900hp (600 motor + 300 nos = 900 total), even gutted and back-halved the way it is, I doubt that v8 Mkiv will do better than high 7s.

So given those points, I find myself struggling to determine a point to that whole project. To be totally honest with you, I feel it would be far more appropriate to put a 2jz-gte into a 'vette or 'stang or viper chassis. Really!

Please explain...

i'm not the owner of this car but as they stated on the forum i think the reason for goin the V8 way was because of cost which i totally understand since this was done basically in someones backyard. also the builder has experience with other V8 engines so it was just the easier way to go.

I appreciate the additional info, but to me it still doesn't make sense. A bone-stock 2jz-gte bottom end is good for 1000hp. Why not just stick with that, and not worry about needing any engine internals expertise, or the expense of aftermarket parts (even v8 aftermarket race internals aren't cheap - nothing like a Toyota engine bone-stock parts anyway)?

I'd have to agree with the 2JZ being more than ample for drag racing.

If I was to do an aggressive weight reduction campaign, I think I'd prefer a NA V8 on a road course, though.

Are you sure a v8 would weigh less than a 3L inline 6 with a 61mm single turbo?

No, it would likely be heavier. No argument there. However, if I was trying to lighten the Supra to offset that weight gain, the added torque is well worth it in my opinion. Of course, you'd have to do serious weight reduction, I'm not talking about swapping the battery, wheels and seats =)

The super GT Supra utilized the V8 in the later years of its racing career. The hybrid one currently does as well. It's all about blasting that torque coming out of corners :)

Anywhoo, just my two cents.

Common misconception: turbos build plenty of torque. :)

Where I can agree with you is that turbos bring that torque on less consistenly/predictably than n/a. That predictability is desireable when you're at the bleeding edge of traction coming out of a corner.

Yep exactly. Not only do V8s build torque more predictably, but they do build it faster. It's instant, which is what you want. Turbos can certainly out torque V8s (and do so very frequently), but even small ball bearing turbos need an instant to build that torque.

Actually v8s don't necessarily build torque faster...at higher rpms, turbos can spool almost instantly. In fact, the only reason turbos aren't roadraced much is because that instant torque-boost can (and does) actually come on instantly (albeit unpredictably) mid rpms...and that unpredictable instant torque-boost does cause traction loss mid-corner.

Regardless, a NA V8 will always have better response and build torque faster than a FI 6. The sudden spike of torque from a turbo is predictable, actually, it's just not as stable as instant torque that increases more linearly. Not saying a FI 6 can't put out crushing torque early in the power band (for example with two small and fast spooling turbos), it just has more of a delay (doesn't matter how relatively small or not that delay is, it is still *there*).

Even a big block, high compression v8 does not have a vertical torque curve. My point is that "early in the power band" is irrelevant - just downshift. At higher rpms (relative to turbo size) torque increases just as fast as with a larger displacement n/a, if not faster.

Yes, but torque starts at a higher point in a larger NA motor, because it comes quicker when you first hit the gas. As I've already said earlier, a FI turbo'd motor can easily put out more torque but there is no way you can rationally argue that a turbo'd engine has the same response and instant torque as a larger naturally aspirated engine.

It appears that we can't come to an agreement. Perhaps you should go over to Toyota and tell them they raced the Supra incorrectly all those years, that a 6 cylinder is the better set up. Or the current Supra hybrid entering in LeMans soon. Or even better, go over to Nissan and tell them the same thing since that's what they also use a NA V8 in their GTR race car!

Or how about this: you're right. Feel better? Good night, chap.

No need to get stressed - I thought we were having a good, objective, friendly discussion. Apologies if I offended you.

Regarding Toyota's super GT racing, or any officially-sanctioned race event, there will be rules. Things like boost, displacement, weight, modifications, etc. are highly regulated. I'm sure Toyota was 'correct' in their setup, based on the rules & restrictions they had at the time. All that said, I wouldn't say they should have run a turbo (even if a rule was the only torque-related reason they didn't) - as I've already stated, turbos aren't ideal for roadracing due to their somewhat inconsistent power delivery relative to rpms.

No worries. I'm not sure why Toyota went with the V8 (after initially going with a 4 cylinder in the early years of JGTC), I always thought the main reason was simply response. Besides the angle you mentioned, which was more predicable and stable power delivery, I don't know what other advantage a NA V8 would have over a FI 6 - esp one as great as the 2JZ.

Have a nice weekend.

I have a bit more info on that. Toyota chose to replace the 2jz with a v4 because of JGTC boostXdisplacement restrictions. Running the 2jz with enough boost to overcome its weight difference over a v4 would have been against the rules. Running it with a low enough boost level to comply with the rules would have made it non-competitive. The v4 conversion also allowed the center mass of the engine to move rearward in the chassis (vs. the I6), which had a positive impact on handling.

It's really a shame. As you're well aware, at higher boost levels, the 2jz really shines. On race fuel and a few tweaks, an mkiv tt 6spd with the oem twins is capable of 450rwhp+. At the time, HKS had a prototype sequential twin turbo, with larger-than-oem turbos. For whatever it's worth, I firmly believe a 2jz-equipped jza80 could have done extremely well in JGTC. It was only that series' rulebook that kept the 2jz out of the limelight. :(

Sincere hopes you have a great weekend too!