n42 vs p90

[m1ghtymaxXx]

So i'm planning a turbo swap for this winter, and its time to start hunting for parts. I still am not sure weather i will be finding an l28et to drop in, or turboing my existing motor. Anyways, i found an l28e locally, from a 1980, with a n42 head. The price: a 24 or rickards. Sounds like a good deal to me, but i'm not to sure how usefull the motor would be to me, especially considering the hassle of transportation and storage. From what i (re)searched on hear, the the p79 head thats in my 83 cannot handle boost, something to do with a coating in the exhaust ports. How does the n42 compare to the p90 performance wise?

 

And lastly, would this motor have egr? I am looking for a non egr intake manifold so i can clean up my engine bay somwhat. Plus it would be nice to have a spare manifold, so i can get started on cutting out the webbing, polising, and adding a 60mm tb and billet fuel rail.

[JSM]

First part I can't answer, but I pretty sure only the 75 came w/a non-egr intake. Unless it was an out of US intake.

[naviathan]

Yes the engine would have EGR. The N42 and the P90 are comparable in performance when worked. The P90 off the factory floor is better flowing though.

[m1ghtymaxXx]

Well i also have a line on a 82 turbo parts car. Would that be a p90 head?

 

I talked to a few local who have swapped l28et's into there s30's, and they say its cheaper and less hassle to just turbo my motor, as i would use very few parts off the stock motor (f.i. parts, dizzy, ecu, etc.) I think it would be work to to pick up the parts car (which i can get for less then 1k), swap the engine in, and work from there. Whats your opinion? Reliability is a big factor too, as this is my summer daily driver.

[ww]

Using a complete turbo parts car to swap the complete driveline, wiring harness and ECU is the easiest and "CAN BE" the least costly swap, especially if you're not planning on any additional upgrades like an intercooler or increasing the boost over stock. Good running turbo donor vehicles have been had for under $500.

[johnc]

Shoudl I just close this thread now or wait to see how bad the N42/P90 debate gets?

[Mack]

eh, give it another day.

 

as to the original poster, I am pretty sure the P79 can handle boost just fine. the liners are cast into the head, Ive see a few come out or become loosened but as far as worrying about it going through a turbo or something, it would first have to work its way through the exhaust manifodl with all its bends. not likely.

 

as far as an N42 or P90? P90 with dish tops will lower CR to 7.4:1. thats factory turbo car compression. If your not going crazy for HP numbers, keeping an N42 on a dished piston block will keep your compression at 8.3:1, which would make for a LOT better off boost response.

 

As far as the 1980 engine, if it is a 1980 engine, it should have an N47 head, which is the exact same as an N42 head, except that it has the exhaust liners (just like the P79).

 

BTW, I have a complete N42 head and will have a complete, non-webbed, non EGR intake for sale shortly. I also have a 300ZX T3, 280ZXT exhaust manifold and all of the J-pipe crap.

 

And I frequent trips to Fargo, every once in a while.

[Forrest]

My p79 handles boost just fine.

[BRAAP]

Shoudl I just close this thread now or wait to see how bad the N42/P90 debate gets?

 

[zeiss150]

Well, here go's...

 

I have an N-42 head on my F54 flat top block now. Im going to swap to a P90 for my turbo. With the flat top pistons my CR would be over 9:1 with a 2mm steel head gasket, thats just a little to high for that head under boost (so I've been told) With the 2mm steel head gasket and the P90 I will wind up with 8.2:1 CR with a much better head for boost. The N42 is an "open chamber" design which is much more prone to detonation than the P90 is. Detonation is the worst thing you can have on a turbo motor... right? a few seconds of pinging under boost and you can kiss your pistons goodbye.

 

If you want higher CR with the P90 head then use the HKS 1mm head gasket that should put you closer to 8:1 CR.

 

As for the question of what is cheaper and most reliable ... ummm .... get a doner and frankienstine it.

 

I'm sure someone will tell me all the reasons im wrong and how well there N42 has worked for them and someone else will them them how there wrong and so on and so on.....

 

but there it is ... .enjoy

 

"plink plink" <------my 2 cents

[m1ghtymaxXx]

So i'm thinking its prolly not worth picking up the 1980 motort then. The main reason i wanted it was for the intake manilfold, but how rare are these 1975 manifolds without egr? I will likely be buying that 82 turbo parts car later this summer, which would have a p90 correct. I think i remember reading that only 83's came with the p90 with hydrolic lifters, which it sounds like i should steer away from.

 

And from what i read on here, the p79 has a coating in the exhaust ports which can't handle the extreme exhaust temps of boost, and will peel away and cause havoc on everything.

 

Another question, do all intake manifolds flow the same? or are some better then others?

[johnc]

And from what i read on here, the p79 has a coating in the exhaust ports which can't handle the extreme exhaust temps of boost, and will peel away and cause havoc on everything.

 

Exhaust temp is exhaust temp regardless of the type of aspiration. If you're seeing temps over 1,400 degrees in the exhaust ports you have some serious problems in the combustion chamber and some stuff flaking off the ports or the exhaust liners is the least of your concerns.

[gottztagetrice]

hii i'm kind of new to the whole z scene but do the manifolds coming off the p90 and n47 line up the same? i understand the p90 can handle more power but how large of a gap is it? i'm shooting for around 300-350 at the wheels. will the p90 be that vital to the car's performance?

[WizardBlack]

hii i'm kind of new to the whole z scene but do the manifolds coming off the p90 and n47 line up the same? i understand the p90 can handle more power but how large of a gap is it? i'm shooting for around 300-350 at the wheels. will the p90 be that vital to the car's performance?

 

You can put the exhaust manifold for turbo (which is square port) on a round port head. I have an N47 and plan to boost it as well.

 

On a side note about EGT's, I have routinely tuned some cars (that are factory turbo'd) that see beyond 900 degrees C (1650 F) on long highway pulls, but I also try to keep short pulls (going up through first 3 or 4 gears) to stay below 860 C (1580 F).

[spork]

For your application, the p79 or the p90 will work fine. If you've got much bigger goals down the line, the P90 is probably a good way to go. For 300-350hp, you could use just about whatever head you wanted to as long as you keep your compression ratio reasonable.

 

On a side note related to EGT's -

Depending on fuel, the car's use and so on, generally I'll tune street cars for around 1500 F for hot but manageable street cars on pump gas. For the more extreme street cars and drag cars 1600-1650 isn't out of the norm, but they tend to pushing big hp numbers, large amounts of boost, and aren't always running pump gas, or if they are, they're using methanol as well.

[gottztagetrice]

great!! thanks for the info guys.. all this has been a big help

[m1ghtymaxXx]

Well fast forward till now, I've got a 83 turbo parts car with 150 000 kms, with a p90. Runs pretty good except for a few small issues (input more than welcome here: http://forums.hybridz.org/showthread.php?t=125172 ).

 

I plan on just doing a straight swap for now, and will prolly have the motor out down the road to fix some rust on the inner fenders, and might do a rebuild then.

 

Off topic, any small jobs i should do to the motor while its out? i'll have the valve cover off to paint it, so obviously it'll be getting a new valve cover gasket.

[TimZ]

Shoudl I just close this thread now or wait to see how bad the N42/P90 debate gets?

I'm staying out