lighten up the mk4 na

881 Views 13 Replies 5 Participants Last post by Xdreamer, Jan 5, 2002

supra4life

Discussion Starter · Jan 1, 2002

the mk4 na is about 200 lbs less than the TT version. A stock TT can run about high 13s 1/4 mile and the stock NA best time is about mid 14s 1/4 mile. With the weigh different, I wonder if there is a way to shave of some lbs and plus a bpu, the NA possible can achieve the 13s range.

Any experts in here tell me if I am crazy or if this is possible.

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vreaux728645

· #2 · Jan 1, 2002

Car & Driver tested a ringer(turbo) that did 13.4 or so in the 1/4! I don't think 13's are too much for an n/a (13.5-13.8, but no one's produced a timeslip to date. The M3 is mighty fast & weighs quite a bit more than an n/a!

There must be some one who with a knowledge of the M3's output curve tha will tune a modified (rebuilt?) n/a to do as well. I know that the n/a does not have the development of the M3, but with lighter weight & some tuning I'd like to believe a peak output could be produced @ the optimum engine speed to get that vaunted mid/low 13 time!

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Soupskees

· #3 · Jan 2, 2002

with major engine work...

i.e. head work, manifold, Jun cams, header,exhaust, gears, short shifter...etc. I have seen a few 13 timeslips.

Can the NA really hit a mid 14 stock? i thought it was like a 15 flat i dunno tho. Also whats the weight of the NA? 3150? or 3445?

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Xdreamer

· #4 · Jan 2, 2002

stock n/a supras are 3251lbs with a automatic transmission. and as for the major enigne work needed do you know if jun makes n/a cams? If so give me some info Thanks Brett

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Soupskees

· #5 · Jan 2, 2002

yeah Jun makes at least an NA cam gear...

i think they make Cams too, of course they are hella pricey and i know there might be a little mod needed on the exhaust(CAM) side.

Oh and are the manuals lighter? (3251)

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DaveH

· #6 · Jan 2, 2002

My car (auto/targa/leather) weighs 3445lb with 1/4 tank of gas. The rollbar weighs 80lb so without that extra weight is would be 3365lb. The only lightening I've done is remove the spare tire.

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vreaux728645

· #7 · Jan 2, 2002

So Soupskees, what type of head/manifold work is involved? The intake & exhaust isn't too bad cost wise, but pulling off the head & the associated machine shop costs could be a BIG deal. JUN cams can't be cheap either! Any chance you could get these runnin' n/a drivers to the forum?

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supra4life

Discussion Starter · #8 · Jan 2, 2002

smaller tires

I wonder if a supra na stock really needs the big size tires(245x50x16). Other similar size and weigh cars do not require that big of a size tires. for example: Lexus IS 300 stock has 215x45x17 and way around. 300ZX stock has 225x50x16.

I am sure you can shave of some lbs being change to a smaller set of tires. This in itself will involve 1/4 miles run.

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Soupskees

· #9 · Jan 2, 2002

there is a port/polished manifold that may also be made by JUn i need 2 check on that

yeah jun cam gears are like 500 a set and i think if u get new forged pistons u can get a really really high compression out of our 3.0 liter.

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Xdreamer

· #10 · Jan 3, 2002 (Edited)

the manual n/a's are 3215 and the uto's are 3251

And as for cam for the n/a you have to get the right type of only really can get them, overseas or have them made.

the cams sold for the twin turbo have a lower duration then what you really need cause it has the turbo puishing air fuel in the mixture where we uses a suction affect the engine makes.

twin tubo your pushing air into the engine

n/a+ air is begin ucked into the engine

So the cams you need have to be m,ade for a n/a in mind no turbo.

but you will need to raise your compression to atleast 12:1

which im currently doing im think of 13:1 but thats going to be to high i think for thstreet plus you n/a will have tp be pulling 9k redline with new cams and what not to make serious power.

so i need valve/spring and titanums retainers are in order.

also when you raise the compression and port/plish the engine you will lose low end torque but gain high end power

i know then new lexus has 10:5:1

compared to are 10:1

its do able if you really want power id use 14:1 but it would only be race car cause you need higher octance and race fuels so you detonate. plus you willl have o do some porting on the exhuast manfiold or get a japane 6:2:1 race header but after thje time your done you could have had sinlge turb supra which wuold give you about the same power poralby more depednig on varaitions . dpends on budget plans for the car. Also the exhuast cam uses a distributr cam gear. So you will have to mod this

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vreaux728645

· #11 · Jan 3, 2002

From my references, raising the compression ratio increases torque by about 4% per whole # increment. As far as the powerband, street engines are usually tuned for low & midrange performance.

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Xdreamer

· #12 · Jan 3, 2002

you say torque increases? meaning if i went with 12:1 i would see a 8% increase in torque? And if you add alot more air and have say a 3" inch exhuast you will lose torque. Thanks For the post and let me know

I wasnt sure if raisng the compression made more torque now i know.

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vreaux728645

· #13 · Jan 4, 2002

Thats what "tuning" is all about. How much power can you make & where do you want it. Thats also what those butterflies are for- a particular power curve. Note: since the IS300 racer will be operated @ high engine speeds, there's no need for vvTi and it doesn't have it! If you want to pass on the road atarting from a midrange rpm, go with a non turbo for your n/a, if its all out power at high rpms the tt ones may be the trick. Watch out for super high output developing cams too. High peak could mean soggy bottom end & soso midrange in the extreme cases.

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Xdreamer

· #14 · Jan 5, 2002

that butterfly you are talking about is it open or closed at wot?

And wouldnt taking out make me loss alot of low end but maybe ill gain the top? I dont want to take it out until im sure. Thanks Brett

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