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Is this cam going to screw up a turbo L28 motor?


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Here pictured is the spec card from the cam in the motor that will be going into my car.  I have ridden around in the donor car, and it seems to run fine.  However, the .480/.480 lift and .274/.274 cam profile seems to match that of a Schneider stage 2 NA cam as sold through MSA.  I believe that the overlap on this cam is 54* and I know that less overlap on a turbo is better, I am just ignorant as to how much is acceptable, and the opinions out there seem to conflict.  The MSA/Schneider Turbo Stage 1 has only 27*, but jeffp in another post says that he runs 54* and it works fine.  I don't have a very free exhaust flow, just your standard turbo exhaust manifold to a T04E 60 to a 3in to a Monza tip.  This car is for the street, but hope to run 15psi.  Priority 1 is not blowing my motor, priority 2 is power.

I know there is a lot of info and discussions on cams out there.  What I am looking for are answers specific to my application.  In short, should I run this head as is?  Would I just be better off selling this N42 and getting a rebuilt stock P90 with a stock cam?  If I go that far should I go ahead and get a stage 1 or 2 turbo cam with it? 

Thanks!

 

post-45034-0-66876500-1414691965_thumb.jpg

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It'll run fine. "Spool time" will suffer a little, but you will make more power on the top end than a smaller cam.

 

You should see 270-300RWHP at 14lbs once the ECU is dialed in, but I would not expect full boost until 3000-3200RPM. The problem with 54* of overlap is that you will loose some idle vacuum, so the power brakes will be weaker. It will be a little soft under 3000RPM, but the cam will come on about then, and then you'll spin up the compressor so then your boost comes in right behind it...expect a big push.

 

Hope you don't intend to use the stock ecu with that cam, however...

Edited by Xnke
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I'm not 100 percent on this, but I think you lose a lot of efficiency boosting carbs.  Not saying it isn't possible, but the boost curve is usually a pain to get right with the af/r's.  If I were you I would just go as rich as I could throughout the band and advance my timing to as close to detonation as safely as possible.  I would look for a super charger..... ;)  just sayin'.  These are just my pennies, and I might be wrong....anyone? 

 

That's also a lot of overlap...I agree with the bit of lag you will experience.  Just keep them revs HIGH!

Edited by godzeerah
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Godzeerah, if I was running a car tech box (really just a box, nothing inside, you would be right, super rich would be the way to go. The HKS on the other hand is a brilliantly engineered piece (there has been a lot written on this site about it, and the airflow computer mapped). It pressurizes the floats under boost, so carbs jetted for the engine NA will run fine boosted (to at least 12 psi) Tony D once ran such a setup and got 17mpg in aggressive daily driving with 300 or so to the wheels, not too shabby :)

(You do still have to rejet for altitude, ambient temp etc. and tony d did go ITBs in the end, but I just am in love with the idea, and sound, of blow through triples)

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That sounds pretty bad a$$ then.  Sounds like the mikunis would be a great setup then, because those suckers flow great anyway, I couldn't imagine what they'll do over atmospheric pressures.  I wouldn't worry too much about the camshaft.  The overlap will bleed some boost, but it should lower your egt's in the process.  You might lose some low end, but I think you'll like it.

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Most I personally saw with an HKS Box was RS OKI on their Dyno eddy-current verified (and likely from an early tuning run) was 444kw on 50's driven on the street, twin turbo (hey, it was the 80's!) and a 125mm exhaust in an S30.

 

There were those who made more, and likely that sticker was low for ultimate development given it's performance. Real racers don't usually put their real HP on the back window...a good example is Electramotive back then with "750 HP@7,500 rpm @ 20.6 psi boost" huh uh, huh huh huh, yeah, right! Considering they boosted to 30+, and revved same as the N/A guys to 9,000+ those were good "keep 'em guessing and smile for the reporter, guys" numbers!

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