Nissan 370Z Forum - Forced Induction Compression Ratios

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Nissan 370Z Forum (http://www.the370z.com/)

- Forced Induction (http://www.the370z.com/forced-induction/)

- - Forced Induction Compression Ratios (http://www.the370z.com/forced-induction/132766-forced-induction-compression-ratios.html)

Elmo370z

01-08-2020 04:39 PM

If closed decks blocks are the end all answer I’m sure we would see a lot more Z’s beating the dog shot out them. 800+whp. I had a buddy who had a closed deck block, and blew a HG a week after the build, his car came from a very well known Gtr shop in Ga.

Hotrodz

01-08-2020 04:46 PM

The bottom line...it is more about the block itself. I may not be able to take a beating at the 800whp+ regardless on how much the cylinder walls are reinforced.

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Martijn_b

01-08-2020 04:53 PM

What about knock sensitivity on octane 93 (not talking E85 here), high compression ratio and super fast spooling twin turbos?

I cant run 12 degrees of timing on even 8psi and go WOT with 3000 rpm or I'll run into timing retard issues with my stock compression ratio. Whilst modern cars can? A built engine wont change that right? But lowering compression will?

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Elmo370z

01-08-2020 05:21 PM

Quote:

Originally Posted by Hotrodz (Post 3899645)

The bottom line...it is more about the block itself. I may not be able to take a beating at the 800whp+ regardless on how much the cylinder walls are reinforced.

Sent from my SM-G965U using Tapatalk

I pretty confident a properly sleeved block will be able to handle that abused far better then a closed deck block. Just ask your engine builder.

Elmo370z

01-08-2020 05:22 PM

[QUOTE=Martijn_b;3899647]What about knock sensitivity on octane 93 (not talking E85 here), high compression ratio and super fast spooling twin turbos?

I cant run 12 degrees of timing on even 8psi and go WOT with 3000 rpm or I'll run into timing retard issues with my stock compression ratio. Whilst modern cars can? A built engine wont change that right? But lowering compression will?

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Who’s your tuner?

Hotrodz

01-08-2020 05:30 PM

Quote:

Originally Posted by Elmo370z (Post 3899650)

I pretty confident a properly sleeved block will be able to handle that abused far better then a closed deck block. Just ask your engine builder.

LMAO, I am counting on it! There is a lot of speculation and I am hopeful that better minds will prevail but so far there is little evidence. The one motor that I am familiar with that has sort of held up has constant over heating issues. I am not looking for four digit whp numbers or close to it. 700 to 750 and I am goo to go!

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Spooler

01-08-2020 06:00 PM

Quote:

Originally Posted by Hotrodz (Post 3899652)

You should be fine. Only way to tell is try it and see. A redo is dang expensive.

Hotrodz

01-08-2020 06:11 PM

Quote:

Originally Posted by Spooler (Post 3899654)

You should be fine. Only way to tell is try it and see. A redo is dang expensive.

I hear ya! Just had to stir the pot a little. You have done your homework and so all you, I and Elmo can do is pay our money and take our chances! I am up for it regardless of outcome!!!

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Spooler

01-08-2020 06:22 PM

Quote:

Originally Posted by Hotrodz (Post 3899655)

I hate redo's with a passion. The definition of insanity is doing the same thing over and over again expecting a different result each time.

Gray Goose

01-09-2020 07:32 AM

Quote:

Originally Posted by Elmo370z (Post 3899650)

I pretty confident a properly sleeved block will be able to handle that abused far better then a closed deck block. Just ask your engine builder.

I thought about wet sleeving as well. But I read, in multiple places, that there are temp issues after. I will be driving this on the road as well and do not want temp issues.

Gray Goose

01-09-2020 07:35 AM

Our Idea for closing the block is different than any I have seen. I am off to the machine shop tomorrow to discuss my ideas and see if they can do it.

Spooler

01-09-2020 08:45 AM

Quote:

Originally Posted by Gray Goose (Post 3899727)

I thought about wet sleeving as well. But I read, in multiple places, that there are temp issues after. I will be driving this on the road as well and do not want temp issues.

I have read the same. Most I read about were pushing water. Only one way to do that and that is if the sleeve machine work was not done properly. I would suspect headgasket issues from a sleeve dropping. I am still researching this. Just any old machine shop won't do. Darton East had major issues years ago from what I was reading. The machine shop must have a 3 or 4 axis CNC and the tolerances are a thousandth to 1/2 a thousandth. It has to be perfect.

Gray Goose

01-09-2020 09:38 AM

Quote:

Originally Posted by Spooler (Post 3899745)

Right, I haven't read any info saying that using a wet sleeve has worked in any form.

Between the info out there on sleeves and the info out there on current shops closing decks has made me want to go my own route and try something different. I think our ideas on closing these decks will work, but I will just have to prove that after the build. -- Or I might never get our ideas off the ground. Depends on if I can get a machine shop with the proper equipment to work with me. Unfortunately I do not have a CNC :shakes head:

Spooler

01-09-2020 09:44 AM

Not everybody get's on the forums. High end builds definitely do not. The sleeves are working all the way up to 1200hp with proper tuning on a VQ35DE block and our blocks are stronger due to the way the mains cradle is integrated into the upper oil pan. I am still researching on the best route to take.

Irishrogue

01-09-2020 04:39 PM

Quote:

Originally Posted by Gray Goose (Post 3899619)

What are you guys thoughts on compression ratios when going Forced Induction.

I know most people just keep the stock compression ratio even when rebuilding.

I'm thinking of going 9:1 or 10:1 since I don't have E85 local and I will be running 93 for 95% of my driving. I cannot see it making more than a 10-20 HP difference when using E85 and perhaps no HP loss when using 93 octane, since the timing can be pushed.

I do plan on pushing high boost at some point! I am building this motor to handle big boost and big HP! So the common thought as with most platforms would be to drop the compression ratio.

Thoughts? There is a wealth of knowledge out here and guys who have tried it all.

Thanks

For what it's worth, I went with 9:1 compression on my rebuild and did 685hp 615 tq on 91 octane at 20 lbs of boost. I don't have the low end problem spooler was talking about, I think that's mostly credit to Seb's tuning abilities with the throttle response. From what Seb explained to me the main limiting factor to running higher boost is the intake manifold.

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