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Discussion Starter #1
A thought occurred to me:

I've long decided that turbo boost is the way to get reliable, usable, and streetable 200whp or thereabouts.

Why 200whp? Well, that means that the engine would probably be spinning 230 at the flywheel; which then means a weight/pwr ratio of 10lbs per hp.

10lbs per hp is what I would consider to be the most ideal sportscar ratio (See: Elise). Anything more and it might get a little too difficult to handle... and anything less than 13lb/hp nowadays and you'd be getting outrun by sports sedans.

Now, with a 4agte, this is probably achievable through 9 to 12psi of boost.

Now, I wonder: IS this still understressed for an unopened 4agze? (not twincharge, but will use 4agze longblock)

It wouldn't be hard to make 10 to 12 psi tractable and streetable, but what about longevity? My car currently has 210,000km on a stock 7rib NA and has no sign of giving up *knock on wood* anytime soon. I figure at least 60,000 more kms of redline charging autocross times and mountain passes.

I realize that realistically, you up the power by twofold and there's gonna be more wear and tear on any motor.
But... I do want rebuilds to go over 160,000km (100,000Mi)

So, what do you guys think?

With the pipe dream of 200hp, am I better off making a mk1.5? At least the 3sgte is definitely understressed at that stock level. BOlt ons and you're at 240hp territory...

Hmn.
 

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The 4agze block is supposedly happy to about 20psi (not sure for how long exactly), and 12psi isnt really any biggie, a nevo pulley will run about 14psi and people run them for years and years so i don't see any problem running 12psi as long as you have kept regular services etc.
 

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agreed

paulj said:
The 4agze block is supposedly happy to about 20psi (not sure for how long exactly), and 12psi isnt really any biggie, a nevo pulley will run about 14psi and people run them for years and years so i don't see any problem running 12psi as long as you have kept regular services etc.
I think since we are talking about a rebuild and not a new motor, a 100,000 miles is a good life for a rebuild, no matter how it is prepped.

I don't think that a turbo at 12 psi is going to affect the longevity, as long as the tuning is conservative, regular maintenance, and good fuel. I think the intake temps from an SC at 10 psi (ae92) is probably higher than the turbo at 12 psi.

My current 8.9:1 GZE is a 16 year old motor with unknown mileage, and although the compression may not be the greatest, I recently did a leakdown and was very pleased with the results, I expect that it's got quite a bit of life left in it (knock on wood :) ). During my evil experiments I've subjected this block to some nasty detonation, fuel cut rev-limiting at 7500 rpm and 13 psi of boost, a smoky turbo also dumped alot of oil through this motor, yet the leakdown average is around 5-6%.

I recently acquired another ae92 core which I'm going to build to stock spec. for a spare, since I don't think I'll ever need anything more, these engines are over-engineered.

I think your 200 WHP is a good estimate, at 13 psi my car was getting a little scary, at least for me, but maybe I'm a wuss, haha :)

Neil
 

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randedge said:
ok, maybe 10 is more realistic, no?

That's still around 200flyWHP.
10 psi will make 200 WHP on an 8.9:1 block with good tuning. If I could make 166WHP which equates to around 195 flyWHP at 7.5 psi with my log manifold and puny turbo (junkyard setup), thru a 2.25" exhaust with catalytic and emissions, plus an early tune ...not dialed in at all, I'm confident that 200 WHP is possible at 10psi. I'm certain with a few more pulls I would have broke 170 WHP.

I'm going to tune for 10 psi at my next dyno session, which should be as many pulls as I can manage in a full 2 hour session. I'm fairly confident I'll break 190 WHP, and would like to break 200. Hopefully late mid-late March I'll make it in.

Neil
 

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I have owned and raced both 160whp 88SC (Cusco, etc..) and now a 260whp MK1.5.

The 88SC had very nice balance at the track (road coarse) and was at the limits of what a NON-limited slip, mild street tire (205/50/15 Kuhmo Estsa's) could put down power wise. Any power beyond 160 whp I would think it would really need much sticker rubber and/or a limited slip to get power down out of the turns.

The MK1.5 is a beast to drive at the track. It is scary for a weekend warrior to be able to very easily over power the tires on 60-70mph sweepers in third gear with just slight throttle input. This is with LSD and 225/45/16 (street tire but much stickier than Kuhmos). Don't get me wrong, still very fun, but a little scary at the same time.

You might want to think about the tire setup and possible LSD trans if you are going with 200whp or above. On the street it might not be too bad, but at the track it will be more power than you can probably put down with an open diff. and street tires.

Oh, and I agree about good longevity with 10-12 psi turbo. You are making more power which is harder on an engine, but compared to 12-13 psi from a SC12 (Cusco pulley), you will make much less heat and if tuned properly will last a long time. I had put 40K miles (at 145K total) and 5 track days (driven VERY hard at the track for up to an hour at a time) on my 88SC with the Cusco and all was still good (factory ECU).

Either way, have fun. It sounds like a great project.
 

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Discussion Starter #7
Project? Just a dream so far. I do have two components: A turbo and a manifold, but that's it.
Actually taking a carguy hiatus here - no expensive tinkering till life is sorted out.
 
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