Raising compression
11-28-2012, 12:17 AM
#1
Three Wheelin'
Thread Starter
Raising compression
Curious...What are the pros & cons to raising compression on a turbo from 8.0:1 to say 8.5:1 or greater?
Who's playing with this?
Who's playing with this?
11-28-2012, 12:42 AM
#2
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I have looked at this quite a bit. Higher compression can lead to knock issues but with E85 it opens up options. E85 is a lot more resistant to knock. My new stoker motor will use slightly higher compression to improve off-boost performance and still should be able to run very high boost levels (20-23 psi) without knock (running E85).
Basically higher compression con is additional tendency towards knock, pro is better performance because higher CR allows the engine to extract more energy from a given amount of air-fuel mixture due to its higher thermal efficiency. On a turbo car this will be especially noticeable on off-boost and bottom end torque.
Basically higher compression con is additional tendency towards knock, pro is better performance because higher CR allows the engine to extract more energy from a given amount of air-fuel mixture due to its higher thermal efficiency. On a turbo car this will be especially noticeable on off-boost and bottom end torque.
Last edited by refresh951; 11-28-2012 at 01:03 AM.
11-28-2012, 02:21 AM
#3
Three Wheelin'
Rogue was running 9.0:1, i think, over a year ago; on a N/A block. IIRC, the ring land gave out in one of the cylinders.
So aside from that, I think as you up the CR, in general the chance for things to blow up goes up exponentially. The tune needs to be closer and closer to spot-on, or it's bye-bye turbo engine, and hello LSx!
So aside from that, I think as you up the CR, in general the chance for things to blow up goes up exponentially. The tune needs to be closer and closer to spot-on, or it's bye-bye turbo engine, and hello LSx!
11-28-2012, 10:48 AM
#4
Three Wheelin'
Thread Starter
Refresh951 & Black51, Thanks for the info., I may stick with stock CR. Too much risk if things aren't spot on. I was thinking of bumping CR up to 8.5, but wondered if that will make a noticable change in engine response out of boost.
11-28-2012, 03:02 PM
#5
Drifting
11-28-2012, 09:32 PM
#7
Three Wheelin'
If I were you, I'd PM some of these guys who have experience with this stuff. And of course, it would be great to hear from guys like Sid, Joshua, Chris White, etc... here.
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11-28-2012, 09:46 PM
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What's your goals? You need to have something in mind to have questions like this.
But yes it can be done on e85 with no issues.
It can be done on pump but you'll probably need to lower to boost and i don't think you'll gain much if any. Probably loose.
There's other things that matter to like intake temps. cooler the better..
with higher comp the peak torque will come on later IICR
Josh was running N/A block with N/A pistons on 18 psi day in day out.
9.5:1 CR on e85
the piston ring let go and wasn't because of detonation. Lated ~9 months
PM them to chime in on the thread so it can be turned into a discussion.
But yes it can be done on e85 with no issues.
It can be done on pump but you'll probably need to lower to boost and i don't think you'll gain much if any. Probably loose.
There's other things that matter to like intake temps. cooler the better..
I have looked at this quite a bit. Higher compression can lead to knock issues but with E85 it opens up options. E85 is a lot more resistant to knock. My new stoker motor will use slightly higher compression to improve off-boost performance and still should be able to run very high boost levels (20-23 psi) without knock (running E85).
Basically higher compression con is additional tendency towards knock, pro is better performance because higher CR allows the engine to extract more energy from a given amount of air-fuel mixture due to its higher thermal efficiency. On a turbo car this will be especially noticeable on off-boost and bottom end torque.
Basically higher compression con is additional tendency towards knock, pro is better performance because higher CR allows the engine to extract more energy from a given amount of air-fuel mixture due to its higher thermal efficiency. On a turbo car this will be especially noticeable on off-boost and bottom end torque.
Rogue was running 9.0:1, i think, over a year ago; on a N/A block. IIRC, the ring land gave out in one of the cylinders.
So aside from that, I think as you up the CR, in general the chance for things to blow up goes up exponentially. The tune needs to be closer and closer to spot-on, or it's bye-bye turbo engine, and hello LSx!
So aside from that, I think as you up the CR, in general the chance for things to blow up goes up exponentially. The tune needs to be closer and closer to spot-on, or it's bye-bye turbo engine, and hello LSx!
Josh was running N/A block with N/A pistons on 18 psi day in day out.
9.5:1 CR on e85
the piston ring let go and wasn't because of detonation. Lated ~9 months
PM them to chime in on the thread so it can be turned into a discussion.
11-29-2012, 06:14 PM
#10
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I have had much success with force induction projects utilizing higher compression ratios on several different vehicle applications, including Bisimoto 911 Porsche utilizing a water cooled M96 engine with 9:1 Bisimoto forged pistons. With this higher compression ratio, we have experienced quicker engine response on off-boost and as well great power/torque under heavy loads by increasing thermal efficiency. With proper engine building, fuel octane and refined tuning, it is very feasible for a reliable high horse power setup.
Piston design and coatings also come into play for a reliable force induction application with higher compression ratios. Bisimoto has spent many years working side by side with the engineers at Arias Pistons, innovating and developing forged aluminum pistons to improve flame travel efficiency, provide a lightweight design without jeopardizing integrity and have spent a countless amount of time working with piston coatings. Bisimoto Spec. forged piston kits utilize ceramic coating on the crown to retain thermal energy within the combustion chamber and a moly-based coating to greatly reduce internal friction, while increasing piston life. From testing we have documented a 4% increase in horsepower and as well anti-detonation properties.
For projects utilizing pump fuels, I would recommend investing on a water/meth injection kit. By injecting a 50/50 mixture of distilled water and methanol, fuel octane will greatly increase and intake air charge temperatures can be lowered by as much as 100 degrees F. This will gain a safe tuning environment for increase boost pressures and aggressive ignition timing tune without the worries of knock or detonation. On Bisimoto projects, we utilize AEM Electronics Water/Methanol systems which have proven to be very reliable and consistent. With a map sensor dependent controller, it will progressively inject the 50/50 mixture as boost pressures increases allowing for a smooth transition and easy tuning.
For more information feel free to reach out to us via email or call at the office.
- Julio A
Piston design and coatings also come into play for a reliable force induction application with higher compression ratios. Bisimoto has spent many years working side by side with the engineers at Arias Pistons, innovating and developing forged aluminum pistons to improve flame travel efficiency, provide a lightweight design without jeopardizing integrity and have spent a countless amount of time working with piston coatings. Bisimoto Spec. forged piston kits utilize ceramic coating on the crown to retain thermal energy within the combustion chamber and a moly-based coating to greatly reduce internal friction, while increasing piston life. From testing we have documented a 4% increase in horsepower and as well anti-detonation properties.
For projects utilizing pump fuels, I would recommend investing on a water/meth injection kit. By injecting a 50/50 mixture of distilled water and methanol, fuel octane will greatly increase and intake air charge temperatures can be lowered by as much as 100 degrees F. This will gain a safe tuning environment for increase boost pressures and aggressive ignition timing tune without the worries of knock or detonation. On Bisimoto projects, we utilize AEM Electronics Water/Methanol systems which have proven to be very reliable and consistent. With a map sensor dependent controller, it will progressively inject the 50/50 mixture as boost pressures increases allowing for a smooth transition and easy tuning.
For more information feel free to reach out to us via email or call at the office.
- Julio A
11-29-2012, 07:03 PM
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I've said it before and ill say it again. Water/meth injection is a "cheap" way of making power, with the added weight of a water tank. It's just something else to eventually go wrong. Yes they come with a "fail safe" unit but they need to externally shut off the boost or engage limp mode with IICR you cannot do with out custom software or an EBC that allows external fail safe control.
11-29-2012, 08:34 PM
#12
Three Wheelin'
Paulyy, what exactly do you mean by "cheap"? Cheap as in inexpensive, or cheap as in cheapo? I presume the second option.
Water/meth injection aside, with that being a whole can-o-worms in itself, everything BisimotoSales just said sounds expensive. Of course, if it's gonna be done right, it's very likely gonna be expensive. Otherwise something will be very likely to give out.
Yes, I remember it wasn't a tune problem that caused Joshua's engine's demise. While I can't prove it, my point was that the engine that was never intended to be turbo'ed & running a higher CR than a stock 951 ultimately had a shorter life span than if it were left alone. So higher a CR must account for increased internal wear, like most power increases.
Water/meth injection aside, with that being a whole can-o-worms in itself, everything BisimotoSales just said sounds expensive. Of course, if it's gonna be done right, it's very likely gonna be expensive. Otherwise something will be very likely to give out.
Yes, I remember it wasn't a tune problem that caused Joshua's engine's demise. While I can't prove it, my point was that the engine that was never intended to be turbo'ed & running a higher CR than a stock 951 ultimately had a shorter life span than if it were left alone. So higher a CR must account for increased internal wear, like most power increases.
11-29-2012, 10:54 PM
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Sam,
Cheap as in easy way out.
I'll put it into an example & Options.
e.g
You want 400 rwhp:
Option 1.
Stock bottom end, stock head, stock cams, a bolt on turbo (k27/8 or LR S 53.. something like that (most common), 3" exhaust w standard down pipe, meth injection and boost over 20 psi will get you there.
Will require a custom tune though, Rogue tuning will do it no problem with no extra charge, Not sure about Vitesse, will need to contact John. but i'm sure he's will be the same.
Option 2. Stock bottom end, Worked head (ported polished, bigger valves if you wish, ect.) optional cam (not necessary), a decent turbo, Proper GT series turbo or something with out a kkk replica housing, full 3" turbo back, better intercooler, boost to 18 psi (recommended on pump fuel, 20 psi would be hitting limits) a chip set (vitesse or rogue)
option 2 is more expensive but will get you there with less boost and less things to worry about if done properly.
get my point? if not shoot me a pm
Cheap as in easy way out.
I'll put it into an example & Options.
e.g
You want 400 rwhp:
Option 1.
Stock bottom end, stock head, stock cams, a bolt on turbo (k27/8 or LR S 53.. something like that (most common), 3" exhaust w standard down pipe, meth injection and boost over 20 psi will get you there.
Will require a custom tune though, Rogue tuning will do it no problem with no extra charge, Not sure about Vitesse, will need to contact John. but i'm sure he's will be the same.
Option 2. Stock bottom end, Worked head (ported polished, bigger valves if you wish, ect.) optional cam (not necessary), a decent turbo, Proper GT series turbo or something with out a kkk replica housing, full 3" turbo back, better intercooler, boost to 18 psi (recommended on pump fuel, 20 psi would be hitting limits) a chip set (vitesse or rogue)
option 2 is more expensive but will get you there with less boost and less things to worry about if done properly.
get my point? if not shoot me a pm
11-30-2012, 12:25 AM
#14
Three Wheelin'
Gotchya. Just wanted to make sure we're all on the same page.
And yes, option 2 would most likely be a more reliable motor.
An interesting thought; if one were shooting for 400 rwhp, a feat that has been done with quite a few people now, using displacement, bigger turbos, etc, would it be worthwhile upping CR in this case? This would mean the motor would remain at 2.5L of course.
Hmmmm
And yes, option 2 would most likely be a more reliable motor.
An interesting thought; if one were shooting for 400 rwhp, a feat that has been done with quite a few people now, using displacement, bigger turbos, etc, would it be worthwhile upping CR in this case? This would mean the motor would remain at 2.5L of course.
Hmmmm
11-30-2012, 12:51 AM
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Gotchya. Just wanted to make sure we're all on the same page.
And yes, option 2 would most likely be a more reliable motor.
An interesting thought; if one were shooting for 400 rwhp, a feat that has been done with quite a few people now, using displacement, bigger turbos, etc, would it be worthwhile upping CR in this case? This would mean the motor would remain at 2.5L of course.
Hmmmm
And yes, option 2 would most likely be a more reliable motor.
An interesting thought; if one were shooting for 400 rwhp, a feat that has been done with quite a few people now, using displacement, bigger turbos, etc, would it be worthwhile upping CR in this case? This would mean the motor would remain at 2.5L of course.
Hmmmm
I've you've got e85 local, i'd use that with a decent turbo and 20 psi (still better then meth injection.. look at sid and josh) and you can make 400 rwhp.
You wouldn't need to have more compression, just the right set up.
IICR sid did a high comp 16v motor and he found that there was a limit of power as there was head lift.