Need some Help please
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Teching In
Joined: Jul 2015
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From: In Sunny Alberta Canada
Need some Help please I have a LS3 525HP engine I purchased from GM as a Crate Engine.
I have decided to twin turbo the engine. I realize the compression is too high for Turbos so I am going to be buying new pistons and rods.
I am an old wrenchhead that has been out of this for quite a few years. I am approaching 70 years old so not really familiar with the newest names in Pistons and rods
Any insight from those that have done this is an added bonus
Anything else I should be considering? Cam?
I have not purchased the ECU or TCM as of yet so can play with those later
I have decided to twin turbo the engine. I realize the compression is too high for Turbos so I am going to be buying new pistons and rods.
I am an old wrenchhead that has been out of this for quite a few years. I am approaching 70 years old so not really familiar with the newest names in Pistons and rods
Any insight from those that have done this is an added bonus
Anything else I should be considering? Cam?
I have not purchased the ECU or TCM as of yet so can play with those later
Thread Starter
Teching In
Joined: Jul 2015
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From: In Sunny Alberta Canada
An LS3 525 has a greater than 10.7:1 and I believe thats at least 2 points above what a Turbo engine should be, so 9.1:1 is suitable, any higher than that and you could be driving a grenade, would you not?
Thread Starter
Teching In
Joined: Jul 2015
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From: In Sunny Alberta Canada
Thread Starter
Teching In
Joined: Jul 2015
Posts: 18
Likes: 0
From: In Sunny Alberta Canada
I referenced this before coming here, its a good article.
http://www.xcceleration.com/cr-boost%20101.htm
This is the part that raised my concern. This is using the same turbo for different compressions Ratio's
If you’re running a 9.0:1 compression ratio @ 1 bar you’ll achieve an effective compression ratio of 18:1
If you’re running a 7.5:1 static compression ratio and 1 bar of boost you achieve an effective compression ratio of 15:1.
For the 7.5:1 to reach the same effective compression ratio you need to run .4bar or 5psi more boost. Combined with the fact that you have less “grunt” outside the boost threshold. Less grunt/torque means your engine produces LESS of a bang when the combustion mixture ignites, along with a slower burn due to a less compressed cooler mixture.
So in a nutshell – if you’re running 2.0 bar of boost on a 7.5:1 static ratio your achieving an effective compression ratio of 22.5:1 if you run the same setup with 9.0:1 static ratio you get the same effective compression ratio but with only 1.5 bar of boost and much better drivability outside of the boost threshold and a better spool due as a result.
Of Course, if the compression ratio is too high then the adiabatic effect will cause the mixture to auto ignite – so there is a line to be drawn obviously.
When building turbo engines static compression ratio is actually a bit of a clumsy way of measuring what’s going on because your measuring the C/R at atmospheric pressure not the desired. With that said, a higher C/R engine will produce more power off boost and subsequently spool your turbo slightly faster. You need to aim for a power goal (whatever that is) and spec your turbo setup accordingly to produce the required air at a reasonable pressure & temperature.
http://www.xcceleration.com/cr-boost%20101.htm
This is the part that raised my concern. This is using the same turbo for different compressions Ratio's
If you’re running a 9.0:1 compression ratio @ 1 bar you’ll achieve an effective compression ratio of 18:1
If you’re running a 7.5:1 static compression ratio and 1 bar of boost you achieve an effective compression ratio of 15:1.
For the 7.5:1 to reach the same effective compression ratio you need to run .4bar or 5psi more boost. Combined with the fact that you have less “grunt” outside the boost threshold. Less grunt/torque means your engine produces LESS of a bang when the combustion mixture ignites, along with a slower burn due to a less compressed cooler mixture.
So in a nutshell – if you’re running 2.0 bar of boost on a 7.5:1 static ratio your achieving an effective compression ratio of 22.5:1 if you run the same setup with 9.0:1 static ratio you get the same effective compression ratio but with only 1.5 bar of boost and much better drivability outside of the boost threshold and a better spool due as a result.
Of Course, if the compression ratio is too high then the adiabatic effect will cause the mixture to auto ignite – so there is a line to be drawn obviously.
When building turbo engines static compression ratio is actually a bit of a clumsy way of measuring what’s going on because your measuring the C/R at atmospheric pressure not the desired. With that said, a higher C/R engine will produce more power off boost and subsequently spool your turbo slightly faster. You need to aim for a power goal (whatever that is) and spec your turbo setup accordingly to produce the required air at a reasonable pressure & temperature.
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Joined: Jan 2012
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From: Bowling Green KY
I'm running 11.4 static CR, and 15 PSI. I do run on a blend of pump gas and E85. 20 years ago that CR and that much boost would have been a race only thing. Now that's a street cruiser.
PS. the Commodore 64 is a nice upgrade, the Vic 20, with the 5K ram is a little long in the tooth. Are your using an acoustic coupler too?
PS. the Commodore 64 is a nice upgrade, the Vic 20, with the 5K ram is a little long in the tooth. Are your using an acoustic coupler too?
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Thread Starter
Teching In
Joined: Jul 2015
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From: In Sunny Alberta Canada
I'm running 11.4 static CR, and 15 PSI. I do run on a blend of pump gas and E85. 20 years ago that CR and that much boost would have been a race only thing. Now that's a street cruiser.
PS. the Commodore 64 is a nice upgrade, the Vic 20, with the 5K ram is a little long in the tooth. Are your using an acoustic coupler too?
PS. the Commodore 64 is a nice upgrade, the Vic 20, with the 5K ram is a little long in the tooth. Are your using an acoustic coupler too?
Yes, I splurged
I also got rid of the Cassette Unit and now Using the 5 1/4 floppies...Still saving for the memory upgrade though
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TECH Enthusiast
Joined: Jan 2012
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From: Bowling Green KY
Actually my engine is an LS1. I originally built it to be a high revving high compression NA motor. I was concerned about the compression being too high to add forced induction, until I seen a guy running 13.5:1 CR with 23 lbs of boost, with an LSX block. Yes this guys setup is a pure racecar, and running race fuel, but it shows what it possible.
I remember those days of programming in "BASIC" and "Fortran" then saving it to those audio tapes. I've had all of those types of PCs, TRS 80 color computer, Vic 20, C64, and even a Motorola 6502 powered original Apple, back in the late '70s and early '80s. If I still had them I'd see what they would give me for them at American Pickers. I did also have a 300 baud modem, that you could sit you hand set down on. Motors haven't changed as much as our PC's. There was no web back then, all you could dial into was a "bulletin board", then came AOL. Most of the people on this board don't remember the world before the interwebs.
I remember those days of programming in "BASIC" and "Fortran" then saving it to those audio tapes. I've had all of those types of PCs, TRS 80 color computer, Vic 20, C64, and even a Motorola 6502 powered original Apple, back in the late '70s and early '80s. If I still had them I'd see what they would give me for them at American Pickers. I did also have a 300 baud modem, that you could sit you hand set down on. Motors haven't changed as much as our PC's. There was no web back then, all you could dial into was a "bulletin board", then came AOL. Most of the people on this board don't remember the world before the interwebs.
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Pump 93 here and stock ls1 compression "which I believe is around 10.5 to1 but could be mistaken" on 13-16 psi , held up just fine on the dyno today 8 pulls, at 13 psi with a 5 hours round trip and numerous street pulls at higher boost . Made 609/647 on 13 psi
Thread Starter
Teching In
Joined: Jul 2015
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From: In Sunny Alberta Canada
Actually my engine is an LS1. I originally built it to be a high revving high compression NA motor. I was concerned about the compression being too high to add forced induction, until I seen a guy running 13.5:1 CR with 23 lbs of boost, with an LSX block. Yes this guys setup is a pure racecar, and running race fuel, but it shows what it possible.
I remember those days of programming in "BASIC" and "Fortran" then saving it to those audio tapes. I've had all of those types of PCs, TRS 80 color computer, Vic 20, C64, and even a Motorola 6502 powered original Apple, back in the late '70s and early '80s. If I still had them I'd see what they would give me for them at American Pickers. I did also have a 300 baud modem, that you could sit you hand set down on. Motors haven't changed as much as our PC's. There was no web back then, all you could dial into was a "bulletin board", then came AOL. Most of the people on this board don't remember the world before the interwebs.
I remember those days of programming in "BASIC" and "Fortran" then saving it to those audio tapes. I've had all of those types of PCs, TRS 80 color computer, Vic 20, C64, and even a Motorola 6502 powered original Apple, back in the late '70s and early '80s. If I still had them I'd see what they would give me for them at American Pickers. I did also have a 300 baud modem, that you could sit you hand set down on. Motors haven't changed as much as our PC's. There was no web back then, all you could dial into was a "bulletin board", then came AOL. Most of the people on this board don't remember the world before the interwebs.
I still have my original Vic 20 and Commodore 64 in the box and the "Pong game" its set up in my man cave. Every guy over 60 knows Pong so its a big hit
After that I had an TRS80, then APPLE !!
If you were Fortran then you are a Punched Card Loader..another thing that is Braille to the young-uns
Then again, old electronics guys like myself are more into vacuum tubes than old computers......
If not comfortable with boost and high static compression ratio, I'd go ahead and swap rods and pistons. You will have a stronger engine, the tuning window should be larger, and it won't lose any power to one with higher CR.
If not comfortable with boost and high static compression ratio, I'd go ahead and swap rods and pistons. You will have a stronger engine, the tuning window should be larger, and it won't lose any power to one with higher CR.
Thread Starter
Teching In
Joined: Jul 2015
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From: In Sunny Alberta Canada
Then again, old electronics guys like myself are more into vacuum tubes than old computers......
If not comfortable with boost and high static compression ratio, I'd go ahead and swap rods and pistons. You will have a stronger engine, the tuning window should be larger, and it won't lose any power to one with higher CR.
If not comfortable with boost and high static compression ratio, I'd go ahead and swap rods and pistons. You will have a stronger engine, the tuning window should be larger, and it won't lose any power to one with higher CR.
Would the cost too go lower compression be about equal to going heavy monitoring? What I mean by that is if I am not building a grenade with Two turbos and 10.7:1 then is there equipment available to monitor boost and or adjust to shut down before grenading?
So some sort of software monitor much like a rev limiter for ignitions?
If so, would that alleviate the concern I have or is the concern I have not really a concern ?
So lets suppose money is not a limiting factor here...what would you do if that was the case?
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From: Bowling Green KY
I wouldn't have built my engine to the CR I have now, if I intended to make a turbo motor out of it. It is just what I had at the time. I took the "run what you have route". It is not really a monitoring issue, it is more of what you can do. If you have lower compression it gives you more flexibility in terms of timing, boost, and fuel octane to work within. I'm in a smaller window with my compression. I need E85 or a lot of meth injection if I were to run pump gas, and I have to be more conservative with timing, and I'm maxing at 15 psi boost.
If it were me, and E85 were readily available, I'd run with your 10.7ish CR. If there were no E85 available I've probably swap the pistons. E85 makes a huge (quoting Trump here, hehe) difference vs 93. My engine used to knock a little under some conditions, even NA on pump 93, E85 it never knocks that I've seen on a data log.
You will have monitoring equipment of some type either way I would expect, either stock knock sensors or something more like a Plex knock sensor for tuning, to make sure your not knocking. As long as you get your timing map right, your knock sensors should take care of any occasional abnormal situational light knock, like a very hot day and low rpm, high load etc.
If it were me, and E85 were readily available, I'd run with your 10.7ish CR. If there were no E85 available I've probably swap the pistons. E85 makes a huge (quoting Trump here, hehe) difference vs 93. My engine used to knock a little under some conditions, even NA on pump 93, E85 it never knocks that I've seen on a data log.
You will have monitoring equipment of some type either way I would expect, either stock knock sensors or something more like a Plex knock sensor for tuning, to make sure your not knocking. As long as you get your timing map right, your knock sensors should take care of any occasional abnormal situational light knock, like a very hot day and low rpm, high load etc.
Thread Starter
Teching In
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From: In Sunny Alberta Canada
Lots of E85 where I live in Alberta.
I understand the principles of the timing map and even how its developed and downloaded into the ECU, my issue is it would seem to me you would have to dyno it to develop a map that is truly the best you could do. Not much interested in Dyno's so is their a mathematical way to approach this or are you playing with a grenade.
I intend on dedicating the full power of the Vic 20 (with memory module) to this task
I understand the principles of the timing map and even how its developed and downloaded into the ECU, my issue is it would seem to me you would have to dyno it to develop a map that is truly the best you could do. Not much interested in Dyno's so is their a mathematical way to approach this or are you playing with a grenade.
I intend on dedicating the full power of the Vic 20 (with memory module) to this task
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Joined: Jan 2012
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From: Bowling Green KY
I developed much of my timing map driving the car on the street, data logging, and watching for the computer to retard timing if it seen knock. If the computer seen knock, I took timing out of the map where the computer pulled the timing. If all was good, I put timing into it until I a little knock, then backed it off a couple degrees. Same idea as we used to advance the distributor till it would just start to ping, then turn it back a little. Getting the timing for really high output area of the timing map however was done on a dyno. for safety reasons. I would also feel comfortable doing it at a race track, however it is risky to do that on public roads. Even with a Vic 20 data logging it. Now maybe if I were up in the boon docks like Ft. McMurray I could find an abandoned road that might work.
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Using an aftermarket controller will allow you to setup many fail safe limits to keep from making ashtrays for the man cave!
BTW - glad to have transitioned from fortran, card readers, washing machine sized hard disks to this crazy world of smart phones etc. Applied knowledge (i.e. wisdom) rules!
TECH Enthusiast
Joined: Jan 2012
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From: Bowling Green KY
I use HPTuners for tuning software. It is capable of real time tuning with some ECU's. However mine is not one of them. So I data log. Later I review the data log, then make updates to my calibration file, then upload it to the ECU.