240zprace Posted March 13, 2004 Share Posted March 13, 2004 on my z is the turbo motor (p90 head & f54 turbo block). i want some opinions on this and why you prefer that head.... 1. i am thinking about getting a full port & polish & valve job done on the head. i've already bought some performance springs/ retainers and a web cam already. 2. i have the choice of doing the work on a p90 or n42 head. 3. i know the compression on the n42 on my turbo block is going to be 8-8.5:1 compression vs p90 7.4:1 4. tell me why you would choose that head and why... need expert advice please. Quote Link to comment Share on other sites More sharing options...
rreford Posted March 15, 2004 Share Posted March 15, 2004 still running a turbo on this motor? would make a difference in the choice. one point to watch on the n42 is cracking between the #3 & #4 cylinders - common problem. Quote Link to comment Share on other sites More sharing options...
Clifton Posted March 15, 2004 Share Posted March 15, 2004 IMO the whole point of a turbo is to run as much psi as you can safetly and make as much power as you can. The more volume the more a/f you can stuff into it. You'll make more hp with the P90 as there is more volume to combust. You will have to run more psi to get it though. The added off boost torque from the higher c/r isn't worth it on the N42, these cars are light enough not to suffer from a 7.4 C/R when off boost. I have used both N42 and P90 and enjoy running 22 psi with the P90. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 26, 2004 Share Posted July 26, 2004 IMO the whole point of a turbo is to run as much psi as you can safetly and make as much power as you can. Well it is an opinion and you are entitiled to it, but I have to disagree completely! Peak power is quite irrelevant! Unless you are using it at as marketing tool, or for bragging rights anyway. It has relatively little effect on how fast a car is, how nice it is to drive or how it responds. By raising CR from 7.4:1 to 8-8.5:1, throttle response will improve, spoolup will be faster, off boost ecomony (ie: 90% of your driving) will be better, and you will most likely have more area under your torque curve. What the result will be is a much more drivable, efficient, and possibly faster car. Certainly faster if your gears are not set up in such a way to take advantage of a peaky engine. these cars are light enough not to suffer from a 7.4 C/R when off boost. I agree that the light platform minimises the drawbacks from a 7.4:1 CR. However, on anything but a drag strip the extra CR would make the car respond much better. If a lower CR is better for power, how come we don't hear about racers dropping their CR to 7:1 in order to make more power under boost? (even drag racers in this case) Obviously the law of diminishing returns applies here. The turbo industry has pretty much settled on the fact that 8-8.5:1 is optimal for most turbo engines. Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 27, 2004 Share Posted July 27, 2004 Drag racers run C16. I can't afford to run 114 oct on a daily driver. I'm stuck with 91 oct. I have run 9:1, 8.3, and 7.4:1 on L motors. I have always run on the edge of detonation. While the 9:1 and 8.3:1 motors were fast they don't compare to the 7.4:1 motor. I can run 20 psi on pump. I just stacked the head gaskets on my 7MGTE motor to run more Boost. Stock is 8.5:1. With the long stroke it should have put me in the high 7's, real low 8's. I was at 17 psi until summer hit. I had to drop to 14 to keep it from knocking. I can now run 18 psi with no knock and it pulls harder than at 14psi. don't even notice the drop in compression. On my Toyota truck with the 3VZ V6 I could only run 12 psi with 1/2-3/4* retard(MSD) per PSI this is with 9:1. I stacked the HG's. I now run 17 psi with the same timing. I now need a stronger clutch as the stock one will not hold above 15 psi. I never had a clutch issue before, ever. Less compression and more psi has made more power in every engine I have had. This is not an opinion. The industry is selling to average Joe. He doesn't want a big laggy turbo that makes alot of power up top, he wants smooth power wich can be had with a small turbo and 7-10 psi and 8.5:1 reliably all day long. I want insane 2nd and 3rd gear roll on tire smoking burn outs on pump gas Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 27, 2004 Share Posted July 27, 2004 Well certainly we all have our preferences, but I felt the discussion wasn't complete without at least presenting both sides of the arguement. Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted July 27, 2004 Share Posted July 27, 2004 P90 81zxturbo 95slobaru impreza Quote Link to comment Share on other sites More sharing options...
ToplessZ Posted July 27, 2004 Share Posted July 27, 2004 What about the E88 with porting and larger valves. Joel the guy selling his killer turbo stroker engine has one of those. Ported by rebello. Id like to know why that is such a good idea? Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted July 28, 2004 Share Posted July 28, 2004 I guess what kind of power do you want? Quote Link to comment Share on other sites More sharing options...
ToplessZ Posted July 28, 2004 Share Posted July 28, 2004 Id say the kind of power that makes your car move.....LOTS- Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted July 28, 2004 Share Posted July 28, 2004 What about the E88 with porting and larger valves. Joel the guy selling his killer turbo stroker engine has one of those. Ported by rebello. Id like to know why that is such a good idea? I would give Dave a ring and ask him why he chooses the E88 for his turbo builds. When I was looking for a reputable L6 builder, Rebello's name kept showing up in all my searchs, so I gave him a call. I don't remember what all the reasons were for his opinions on using the E88 for a stroker turbo motor, so thats why you should get ahold of him. He's a very nice person to speak with, and would answer this question for you I'm sure. I'm not picking one head over another, saying either is better, its just he recomended the E88, with his turbo port, and larger valves to me, and thats the choice I made. I use the 1mm HKS gasket, and get a 8.5 to 1 comp ratio, which gives great off boost throtle responce on 93 oct gas..... Try this email address, its the last one I had for Rebello; DReb993524@aol.com Quote Link to comment Share on other sites More sharing options...
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