High compression and low boost?
02-05-2011, 09:03 AM
#41
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The first post I ever made here was in regards to the suitability of boosting my 10.5 comp motor and i got flamed pretty good. Lots of research later and Im almost ready to shove some boost in.
My build includes a very well prepared bottom end (I rev it to 8500 rpm every day many times) big cams, big valves and extensive head work at 10.5:1 and a relatively small turbo. Im currently atmo on e85 and running stupid amounts of timing (well over 35 degrees in places) and when boosted i will lose some of that and hopefully 10-12 psi will take its place, but psi IS just a measure of restriction. And remembering this, 10 psi on my very well breathing engine (compared to most of the stock head cars here) could well be like pushing 14psi at the same AIT as many other cars here, certaintly in terms of actual air mass flowed.
Dann
EDIT: lets not forget how hard my 10.5:1 engine with highly worked heads will spool a small turbo, on the street and tarmac rally it should be awesome.
My build includes a very well prepared bottom end (I rev it to 8500 rpm every day many times) big cams, big valves and extensive head work at 10.5:1 and a relatively small turbo. Im currently atmo on e85 and running stupid amounts of timing (well over 35 degrees in places) and when boosted i will lose some of that and hopefully 10-12 psi will take its place, but psi IS just a measure of restriction. And remembering this, 10 psi on my very well breathing engine (compared to most of the stock head cars here) could well be like pushing 14psi at the same AIT as many other cars here, certaintly in terms of actual air mass flowed.
Dann
EDIT: lets not forget how hard my 10.5:1 engine with highly worked heads will spool a small turbo, on the street and tarmac rally it should be awesome.
Details?
Also FWIW myself and multiple others on the board do or have run 10:1 factory compression ratio with boost with no more problems than anyone else. At 8ish psi and no timing tuning I was at 190hp on the GT3071.
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02-05-2011, 09:31 AM
#42
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It has a polished crank, knife edged and balanced, something like 22 hours work on it. prepped balanced stock rods, some forgies, all balanced as an assembly, and stainless valves with big springs and solid lifters. actually i lied its set at 8400 rpm redline and i shift at 8000 but i still hit it a fair bit. And on e85 im running more timing than i made out, its in the fourties.
Dann
EDIT: B6 not BP..
Dann
EDIT: B6 not BP..
Last edited by nitrodann; 02-05-2011 at 09:42 AM.
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02-07-2011, 05:28 PM
#45
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Cheers mate,
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
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02-07-2011, 05:31 PM
#46
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Cheers mate,
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
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02-07-2011, 05:53 PM
#47
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Cheers mate,
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
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02-07-2011, 09:05 PM
#48
I think the take-away here is that it is possible, but needs a fantastic tune and that by the time you factor in the loss of timing..you might wish you'd gone with a low-comp engine and more boost. I'm partial to a setup like Hustler's. He has all the torque (from the timing he gets to run) and plenty of boost too (from the low CR).
Put your location in your profile. 
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02-07-2011, 11:02 PM
#50
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You can't arbitrarily run high compression. For a given amount of boost, octane, and intake air and coolant temperature, there's a limit to compression ratio, beyond which your timing can't reach MBT. It's not just a matter of "tune". If you can't reach MBT you're better off running a lower compression ratio.
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02-07-2011, 11:46 PM
#52
You can't arbitrarily run high compression. For a given amount of boost, octane, and intake air and coolant temperature, there's a limit to compression ratio, beyond which your timing can't reach MBT. It's not just a matter of "tune". If you can't reach MBT you're better off running a lower compression ratio.
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02-08-2011, 12:04 AM
#53
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When the engine was built it was never intended to be boosted, it was intended to stay NA to keep it in class for local hillclimb regs. That why money was spent on the crank and not the rods, it doesnt need them in its current form and without the work on the crank it would not take advantage of the cams and other headwork because it just wouldnt rev like it does. Im not keen on replacing the rods with the m-tuned ones because its only 15,000km old and a lot of work was spent balancing it. I only want 200-250rwhp which im led to believe is ok on stock rods (with 250 being on the upper end of safe).
The only question is will this be fast enough for me.
But im sure it will spool great and be a super quick daily and hillclimb car.
Dann
The only question is will this be fast enough for me.
But im sure it will spool great and be a super quick daily and hillclimb car.
Dann
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02-08-2011, 02:05 AM
#57
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Cheers mate,
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
Yeah I didnt think it would be an issue, but I got flamed pretty good when i first mentioned it here, but i think maybe a lot of you guys on the forum dont realise in oz we get 98 octane at every servo and 100 at some. thats what i was planning on using to begin with, but I think now Ive gone the e85 route i should be able to pump in a good 12 or 14psi and make 200-250 with great spool and torque.
Thoughts?
Dann
Most other places go by RON like where you are located. 98 RON is roughly in the 91\93 AKI area. Some other pumps around the US also offer higher aki rated fuel.
If you weren't aware just wanted to make sure you were now
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02-08-2011, 02:55 AM
#58
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Yeah you average ron and mon i was aware, still thought that 93 in the usa was closer to our 95, i did some quick calculations in my head so maybe I'm a little confident based on an incorrect assumption? But as it has been said above I think 250atw on a stock long block is pretty achievable as long as I play it safe with detonation, which will be easy on E85.
Cheers,
Dann
Cheers,
Dann
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02-08-2011, 09:55 AM
#60
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I do 250 on a stock 10:1 block but seriously, it's not fast enough. And the shortblock really has no safety headroom. I'm almost positive the rods are not straight after whatever 40-50,000 miles I've had the turbo on there.
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