Intake and torque peak; engine choices in a light car

Since I'm a big-car guy, I'm all about torque. I can design that kind of engine pretty well, but my buddy and I (tuske427) just bought a 74 Maverick that we're going to strip down and cage for a TransAm-style road racer (and it might get some fat-n-skinnies for one or two drag passes :))

Anyway, the car is 2700 lbs as it is with the 302. After its been gutted, fitted with aluminum heads (trick flow twisted wedge) and intake, headers, a few fiberglass panels, and a 9", I'm guessing about 2300 if that. Most likely a 5 speed manual and a few different ratios for the rear. So I have a few engine design quandries.

I've never built an engine that needed anything but a dual plane intake. Could you take a look at these dyno graphs and tell me what you think? My problem is that Dyno2000 only differentiates between single and dual plane manifold and you have to admit that with products like the RPM airgap its no longer that simple. Here is the chart.

http://www.curtisandkim.com/302dynoall.jpg

-I'm looking at three intakes; Performer RPM or RPMairgap (1500-6500), Torker2 (2500-6500), and Weiand Stealth (idle-7000). Does the stealth really supply decent velocity and flow to cover that wide a powerband?

-Should I maybe consider stepping up to a high-rise single plane like a Victor Jr? I don't mind some cold start issues and other drivability things, but do I really need an 8000-rpm intake?

-Any thoughts on cam? The lowest output simulation uses a cam I made up that is 212/218 on a 110 LSA, roller. The 500 and 540hp simulations used a 224/234 on 110 roller. Lift numbers were all right around 1/2".

-Since I've also never designed an engine for a manual tranny, is the 3500-5000 rpm torque peak just way out of the question? Or will the light weight of the car and low gears make it just fine?

-Should I consider maybe a stroker crank to get my power by 6500 instead of 7250 and be able to drop down a "size" in manifold? Or will the car be light enough that it won't matter?

my head hurts...

...sorry i cant be of any help.

ROFLOL!!!!!!

Sorry, but engine choices for a "light" car I thought would be asking about something in 1600cc to 2000cc range for a sub 1,000kg car, something like an old Toyota or Honda, not a bloody 5L V8!



I can't help much with your engine options, but just looking at your dyno predictions I would go with the 540hp option, It makes more power and torque accross more of the rev range than the other two options, and dosn't appear to be any more peaky.

However, one things I will point out is traction, traction traction!
How are you going to put 500+hp to the road in a 1,000kg car?
You might find the 460hp engine will actualy get you around a track must faster, it has a much flatter torque curve, and the power curve stays nice and flat accross between the 5,500 and 8,000rpm sweet spot.

With a chassis that light you want to think more about controll than out right power.

How are you going to put 500+hp to the road in a 1,000kg car?

Duh... Glue.:rolleyes:

You might find the 460hp engine will actualy get you around a track must faster, it has a much flatter torque curve, and the power curve stays nice and flat accross between the 5,500 and 8,000rpm sweet spot.

With a chassis that light you want to think more about controll than out right power.

Good ideas. Plus the 460hp version would be much easier to tune. Maybe I could even play with cams and head flows to get more area under the curve down low in the RPM band.

The Rally car I crewed on went through about 3 or 4 differnt engine designs with regard to heads, cams, exhaust and Carbs before a set up was found that the driver was happy with.
At its peak the engine was making about 190hp, after it started with barley 150. We settled on about 180hp, which provided the best compromise between out right power and useable torque. In a 700kg Mk1 Escort I personaly attest to its ablity to twist the chassis and lift a wheel out of a corner from only 4,000rpm, well short of its peak power at 8,000rpm and its reline at 9,000.
It idled around a 1,000, needed 2,500 to get the car moving and didnt start to sing till 3,000. But from 4,000 on up it was a dream to drive.
The biggest problem we had was finding a tall enough diff to make use of the power that high up in the rev range.

Another reason you might also want to consider the 460hp engine, the 500+ configurations might be making power and torque that is beyond your reach with the ratios avliable to you, it might come and go in a spurt of disapointment.

Yeah, that's very true. I'm also looking at the charts, and up to 6000 these engines are very similar. I guess what I'm saying is, traction may be about the same off the line with all three; in fact it may be worse with the 460hp since there is as much as 50 more lb-ft of torque at 3500.

I think what may make the decision is $$. If you notice, the 540hp engine is 7500-rpm engine. The 460hp is a 6500-rpm engine. That might make the difference between a stock bottom end and some exotic stuff.

Check out this chart, too. I made some new cams and took the mufflers off for this simulation. This compares a 600-horse engine with the original 460-horse. They are mostly the same engine up until 5500. I think off the line they'll perform very similarly, but the traction problems might happen at about 6000-rpms :) Now, the question is; how to get the engine to hold together until 8000 rpms :D

http://www.curtisandkim.com/302dyno460-600.jpg


Edit: I can also get rear gears anywhere from 2.35 all the way up to 6.30 for the 9", so I hope that will be enough :)

And of course don't forget that the higher in the rev range you get, and the more power you make the more responsive an engine becomes.

At 6,000rpm the differnce between holding 6,000rpm and reving to 7,000 laying out another 100hp is not very much, only the lightest twitch of your little toe.
While that would be lot of fun in a single seater Formula car, it could be a reciepe for doughnuts at 100mph in a converted road car :)


That said if you can afford an engine that will sing to 8,000rpm do it, even if you limits its hp to start with, and work towards the 500+ numbers.
There is something magical about setting a car up, balancing it on the thorttle at 7,000+rpm and just holding it there through a corner.

Well, I'm new to this thing you call "racing," but I looked it up in the dictionary. :D I've taken my street cars to higher performance levels, but they don't outdrive me. Now I'm looking at building a car that will be more equipped to take the punishment.

Thanks for the help.

By the way; the really scary part is that we're keeping it street legal; lights, wipers, the works. Look for me on in the news. I'm sure I'll get a few tickets here and there.

Is that an actual dyno that you posted? How does a 5L V8 rev up to 11k?

*stunned amazment*

I know of a few 500+hp street legal cars, but they are either AWD Japanese super cars, Heavily modified Rally/Targa cars or Drag racers with Huge slicks and tubbed rear ends.
And with the exception of some of the Japanese AWDs, none of them are the sort of thing I would like to spend in time in on anything but a race track!


Curtis your Nuts!

Have fun, keep us updated on what you do and how it works, and make sure your life insurance is up to date.

Is that an actual dyno that you posted? How does a 5L V8 rev up to 11k?
It doesn't. Its just a simulation. There would be no reason to rev this engine past 8000, but these are dyno simulations run on Dyno2000 software. All real dyno charts you see just go up to redline because that's all the further the engine goes. Dyno2000 uses theoretical VE to continue plotting the curve, and it just so happens that this graph is defined at 11,000.
I know of a few 500+hp street legal cars, but they are either AWD Japanese super cars, Heavily modified Rally/Targa cars or Drag racers with Huge slicks and tubbed rear ends.
And with the exception of some of the Japanese AWDs, none of them are the sort of thing I would like to spend in time in on anything but a race track! Curtis your Nuts!

Well, I have a couple over 400 hp, but they weigh 5000 lbs. The daily driver I took cross-country this summer was the wagon and it makes about 420 hp. I guess nuts is a good word for it. I don't know too many guys (in fact none) who have a 600-hp 302 in a 2300-lb car. Sure, it will idle at 1100 and overheat everytime you start it, but it will be FUN. I'll have to actually get this beast on a real dyno and see how it does. Dyno2000 hasn't let me down yet; its always been within about 4% of my actual numbers, but I've never tested it on such an extreme engine. Oh, and by the way, often times dirt oval track cars here are 450-650 hp and 1800 lbs. How they get traction on dirt is beyond my grasp.

Oh, and by the way, often times dirt oval track cars here are 450-650 hp and 1800 lbs. How they get traction on dirt is beyond my grasp.


Its easy, they don't :biggrin:
But they are also purpose built race cars with trick suspension set ups.


It will be an enormous amount of fun though, and I wish I was even close to North America so I could come and play with it :)

Iv driven a 180hp in 700kgs with a full race suspension and slicks around a track, I can only try and imagine what 500hp on road legal tyres on the street would be like :evillol: :evillol:


I still have a feeling however that you might be over powering the chassis ;)

Back in high school I had a 77 AMC Gremlin-X, other guy had a mavrick, allways talking shit. I finally called him on it one day and told him to either race me or shut the fuck up, he wrecked his car the next week and we never got to race.

I think with any of those options your going to end up spending more time tuning the suspension than the motor.