looking for input/opinions on what cr to go with on a 2.3 build?
Jun 8, 2012, 07:26 AM
#1
looking for input/opinions on what cr to go with on a 2.3 build?
So Im piecing and planning my evo back together. The evo is gonna be used exclusively for road course/hpde and some autox. I pretty much decided to go for E85 as fuel of choice.
I am going with MAP's EF3 turbo. Im also going with a mildly ported head and either S2 or Kelford 272s. Next up is what compression ratio to get for the 2.3? I plan on a mild road race tune, probably 25ish psi. Should I just go with 9:1, or would I be better off going with something higher to take the advantage of E85? If I can tune for a bit higher than 25 psi on this setup and not be on a ragged edge tune for road racing I will, but I kind of want the motor to last more than one race.
Im getting ready to buy the shortblock but want to make sure I decide on the right one for me, tia!
I am going with MAP's EF3 turbo. Im also going with a mildly ported head and either S2 or Kelford 272s. Next up is what compression ratio to get for the 2.3? I plan on a mild road race tune, probably 25ish psi. Should I just go with 9:1, or would I be better off going with something higher to take the advantage of E85? If I can tune for a bit higher than 25 psi on this setup and not be on a ragged edge tune for road racing I will, but I kind of want the motor to last more than one race.
Im getting ready to buy the shortblock but want to make sure I decide on the right one for me, tia!
Jun 9, 2012, 05:42 AM
#4
Thanks for responding.
I had just assumed that with a more aggressive cam my dynamic compression would actualy be lower. Going with a higher cr should improve throttle response, and that is a good thing. I just dont want to end up with something so high Im risking detonation issues. Im pretty hard on the car at the track so durability is important.
I had just assumed that with a more aggressive cam my dynamic compression would actualy be lower. Going with a higher cr should improve throttle response, and that is a good thing. I just dont want to end up with something so high Im risking detonation issues. Im pretty hard on the car at the track so durability is important.
Jun 9, 2012, 05:57 AM
#5
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I am kinda surprised that Aaron suggested 9.0:1 for your E-85 tune. I figured that he would advocate a higher static C.R. of at least 9.5:1 if not 10:1 on E-85. Maybe he'll go into more detail as to his recommendation.....just for informative purposes.
Jun 9, 2012, 08:07 AM
#6
9:1 for a few reasons. If you want to switch back and forth between E85 and pump and still make good power on pump, you wont be doing that with a 10:1 or higher.
Bearing life at high boost and therefore high power being the second. It is fairly common to run the car to 18*-19* in the absence of knock but compression adds to bearing forces. I suppose its all how you tune the car but realistically the compression doesnt seem to make as much a difference as is generally attributed to it.
For instance, Mikey's car when it was still twin scroll made 675 at 38psi or so and is a 10.3:1 motor. It cant run more than 19psi on 92 octane, though it did make 470whp at that level. Johnny TSI made 679 at 32psi on a 8.5:1 or 9:1 motor with more or less the same setup but we ran more timing on it (which in turn dropped the boost down to 32psi). Jeff has had everything from an 8.5:1, his current 9:1 motor program, and we have had it as high as 11.5:1. The car is just as fast with a 9:1, or faster, than it was with the 11.5:1 motor. We can safely run more timing on less compression to make the same power but reduce the tendency to misfire.
Bearing life at high boost and therefore high power being the second. It is fairly common to run the car to 18*-19* in the absence of knock but compression adds to bearing forces. I suppose its all how you tune the car but realistically the compression doesnt seem to make as much a difference as is generally attributed to it.
For instance, Mikey's car when it was still twin scroll made 675 at 38psi or so and is a 10.3:1 motor. It cant run more than 19psi on 92 octane, though it did make 470whp at that level. Johnny TSI made 679 at 32psi on a 8.5:1 or 9:1 motor with more or less the same setup but we ran more timing on it (which in turn dropped the boost down to 32psi). Jeff has had everything from an 8.5:1, his current 9:1 motor program, and we have had it as high as 11.5:1. The car is just as fast with a 9:1, or faster, than it was with the 11.5:1 motor. We can safely run more timing on less compression to make the same power but reduce the tendency to misfire.
Jun 9, 2012, 09:30 AM
#7
I know it's a little o/t, but Aaron, for a 2.1 destroked with a 76 mm turbo running straight ethanol 11.5:1 would be a good choice as regards cr? Your opinion would be much appreciated, thanks.....
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Jun 9, 2012, 10:58 AM
#8
9:1 for a few reasons. If you want to switch back and forth between E85 and pump and still make good power on pump, you wont be doing that with a 10:1 or higher.
Bearing life at high boost and therefore high power being the second. It is fairly common to run the car to 18*-19* in the absence of knock but compression adds to bearing forces. I suppose its all how you tune the car but realistically the compression doesnt seem to make as much a difference as is generally attributed to it.
For instance, Mikey's car when it was still twin scroll made 675 at 38psi or so and is a 10.3:1 motor. It cant run more than 19psi on 92 octane, though it did make 470whp at that level. Johnny TSI made 679 at 32psi on a 8.5:1 or 9:1 motor with more or less the same setup but we ran more timing on it (which in turn dropped the boost down to 32psi). Jeff has had everything from an 8.5:1, his current 9:1 motor program, and we have had it as high as 11.5:1. The car is just as fast with a 9:1, or faster, than it was with the 11.5:1 motor. We can safely run more timing on less compression to
make the same power but reduce the tendency to misfire.
Bearing life at high boost and therefore high power being the second. It is fairly common to run the car to 18*-19* in the absence of knock but compression adds to bearing forces. I suppose its all how you tune the car but realistically the compression doesnt seem to make as much a difference as is generally attributed to it.
For instance, Mikey's car when it was still twin scroll made 675 at 38psi or so and is a 10.3:1 motor. It cant run more than 19psi on 92 octane, though it did make 470whp at that level. Johnny TSI made 679 at 32psi on a 8.5:1 or 9:1 motor with more or less the same setup but we ran more timing on it (which in turn dropped the boost down to 32psi). Jeff has had everything from an 8.5:1, his current 9:1 motor program, and we have had it as high as 11.5:1. The car is just as fast with a 9:1, or faster, than it was with the 11.5:1 motor. We can safely run more timing on less compression to
make the same power but reduce the tendency to misfire.
Great advise, straight from a pro!
. I'll take your advise and stick with a 9:1.
Jun 9, 2012, 01:00 PM
#9
If it were a solid block with the SCE headgasket maybe. I wouldnt attempt it on a street car. Like I said before we ran 8.50 @ 165 and 167 with the 11.3:1 motor on a slick launch, we switched back to the 9:1 motor and run 8.40 on a sticky launch (1.25 60') Seems to me the power is there with the 9:1. Everything is off the shelf and easier to get in a timely manner, headgaskets are safer especially with an 87mm bore, all in all lower compression isnt going to hurt you.
Jun 10, 2012, 12:14 PM
#11
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I am wondering what the availability of E85 is in the OP's area. If it is widely available then he might want to consider doing the build with a higher static CR. (10.0:1 is not really much higher than 9:1).
That is, why not do a dedicated hi comp ethanol build backed up by a switchable, "emergency" 93 octane, limp home tune. I am assuming that E85 is widely available at the pumps in Nebraska.
If his build's CR remains at a basically stock 9.0:1 and boost is kept at a lowish 23-25, then any additional power would have to be extracted from advancing the ignition timing.
I really don't see much sense in running 102 octane fuel if boost is gonna be kept so low and the CR is kept stock. In fact, why go to the expense and trouble of upgrading the entire fuel system if you are just gonna run a stockish 9.0:1 compression and a modest 24 PSI?
Heck, he should be able to do that safely on straight 93 octane pump gas. Granted, on any given engine, the E85 can be tuned to produce roughly 10% more power than pump gas on the same total airflow level...but still he would be leaving a gob of safe power on the table.
Since he does road courses he would probably appreciate the instant throttle response available from a high compression build especially at low RPM corner exit speeds before the turbo spools up. I say go high-comp with your large dispacement build especially since you will be keepng peak boost levels relatively low.
I am not a huge fan of resorting to advanced ignition timing as a power provider as it prolongs burn times. High comp basically achieves the same result as earlier spark but with shorter burn intervals. Take advantage of the 10 additional octane numbers and gain improved off-boost, throttle response and lowend torque.
That is, why not do a dedicated hi comp ethanol build backed up by a switchable, "emergency" 93 octane, limp home tune. I am assuming that E85 is widely available at the pumps in Nebraska.
If his build's CR remains at a basically stock 9.0:1 and boost is kept at a lowish 23-25, then any additional power would have to be extracted from advancing the ignition timing.
I really don't see much sense in running 102 octane fuel if boost is gonna be kept so low and the CR is kept stock. In fact, why go to the expense and trouble of upgrading the entire fuel system if you are just gonna run a stockish 9.0:1 compression and a modest 24 PSI?
Heck, he should be able to do that safely on straight 93 octane pump gas. Granted, on any given engine, the E85 can be tuned to produce roughly 10% more power than pump gas on the same total airflow level...but still he would be leaving a gob of safe power on the table.
Since he does road courses he would probably appreciate the instant throttle response available from a high compression build especially at low RPM corner exit speeds before the turbo spools up. I say go high-comp with your large dispacement build especially since you will be keepng peak boost levels relatively low.
I am not a huge fan of resorting to advanced ignition timing as a power provider as it prolongs burn times. High comp basically achieves the same result as earlier spark but with shorter burn intervals. Take advantage of the 10 additional octane numbers and gain improved off-boost, throttle response and lowend torque.
Last edited by sparky; Jun 10, 2012 at 09:21 PM.
Jun 10, 2012, 01:35 PM
#12
I am wondering what the availability of E85 is in the OP's area. If it is widely available then he might want to consider doing the build with a higher static CR. (10.0:1 is not really much higher than 9:1).
That is, why not do a dedicated hi comp ethanol build backed up by a switchable, "emergency" 93 octane, limp home tune. I am assuming that E85 is widely available at the pumps in Nebraska.
If his build's CR remains at a basically stock 9.0:1 and boost is kept at a lowish 23-25, then any additional power would have to be extracted from advancing the ignition timing.
I really don't see much advantage to running 102 octane fuel if boost is gonna be kept so low and the CR is kept stock. In fact, why go to the expense and trouble of upgrading the entire fuel system if you are just gonna run a stockish 9.0:1 compression and a modest 24 PSI?
Heck, he should be able to do that safely on straight 93 octane pump gas. Granted, on any given engine, the E85 can be tuned to produce roughly 10% more power than pump gas on the same airflow...but still he will be leaving a gob of power on the table.Since he does road courses he would probably appreciate the instant throttle
response available from a high compression build especially at low RPM corner exit
speeds before the turbo spools up. I say go high-comp with your large dispacement
build especially since you will be keepng peak boost levels relatively low.
I am not a huge fan of relying strictly on advanced ignition timing as the main power
provider as it necessarily requires longer combustion burn times. High comp basically achieves the same result as earlier spark but with shorter burn intervals. Take
advantage of the 10 additional octane numbers and gain improved off-boost, throttle
response and lowend torque.
That is, why not do a dedicated hi comp ethanol build backed up by a switchable, "emergency" 93 octane, limp home tune. I am assuming that E85 is widely available at the pumps in Nebraska.
If his build's CR remains at a basically stock 9.0:1 and boost is kept at a lowish 23-25, then any additional power would have to be extracted from advancing the ignition timing.
I really don't see much advantage to running 102 octane fuel if boost is gonna be kept so low and the CR is kept stock. In fact, why go to the expense and trouble of upgrading the entire fuel system if you are just gonna run a stockish 9.0:1 compression and a modest 24 PSI?
Heck, he should be able to do that safely on straight 93 octane pump gas. Granted, on any given engine, the E85 can be tuned to produce roughly 10% more power than pump gas on the same airflow...but still he will be leaving a gob of power on the table.Since he does road courses he would probably appreciate the instant throttle
response available from a high compression build especially at low RPM corner exit
speeds before the turbo spools up. I say go high-comp with your large dispacement
build especially since you will be keepng peak boost levels relatively low.
I am not a huge fan of relying strictly on advanced ignition timing as the main power
provider as it necessarily requires longer combustion burn times. High comp basically achieves the same result as earlier spark but with shorter burn intervals. Take
advantage of the 10 additional octane numbers and gain improved off-boost, throttle
response and lowend torque.
There are roughly 5 stations close to me. Nebraska is corn country. One of the nice things about this state is lots of e-85 and no smog testing. I see what John Bradley is talking about, being able to advance ignition timing to compensate and being able to run higher boost.
My initial view was exactly what you are saying. Plenty of e85 availability, and the evo is probably gonna be trailored to tracks that are farther away.
I think the lowest boost I can run with the EF3 is 25 psi, and I see dyno sheets with nice numbers at around that level. I still doing my research but I dont know how safe it would be to push any stock framed turbo 30 psi plus on a road course. Some track events are held in days that can get 90 plus deg weather as well. Like I said, Im still trying to research a good boost level where I can take the benefit of my mods but its hard since most people here use their evo for 1/4 mile.
Having a limp home dual map would be nice but I know for me it would be used solely for an emergency to get the vehicle back home.
For thos times I would autox, the throttle response from a higher compression would be nice, but how much would I gain by bumping up? Im already going 2.3 so would it even be that big of a deal? IDK, soo many choices, I just would hate to regret it later on.
Question though, wouldnt a downside to advancing ignition timing be a hotter cyl temps which in turn means coolant system has to work harder? So that would mean a lower cr engine with more adv ign timing would require that much better of a radiator?
Like I said, these are all questions running through my head and the reason I have a difficult time deciding on a setup. haha.
Jun 10, 2012, 09:44 PM
#13
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i used to want to employ lower comp ratio(8.0:1) in my wish list build reasoning that with anything higher than that on pump gas I would be running into some serious detonation, EGT's. and excessive cylinder pressure issues at anything over 23 PSI.
However, Dave Buschur took issue with me and explained, in a nice way that I was full of myself. He said that based upon his experience, 10:1 is perfectly doable, even on 93 octane pump gasoline, even when running higher boost levels than 23 PSI.
The EF3 is a good choice sure, but I might also take a look at the BBK-B, or the BBK-C even. Don't do any IC smaller than the BR "Race" either.
However, Dave Buschur took issue with me and explained, in a nice way that I was full of myself. He said that based upon his experience, 10:1 is perfectly doable, even on 93 octane pump gasoline, even when running higher boost levels than 23 PSI.
The EF3 is a good choice sure, but I might also take a look at the BBK-B, or the BBK-C even. Don't do any IC smaller than the BR "Race" either.
Jun 11, 2012, 06:11 AM
#14
i used to want to employ lower comp ratio(8.0:1) in my wish list build reasoning that with anything higher than that on pump gas I would be running into some serious detonation, EGT's. and excessive cylinder pressure issues at anything over 23 PSI.
However, Dave Buschur took issue with me and explained, in a nice way that I was full of myself. He said that based upon his experience, 10:1 is perfectly doable, even on 93 octane pump gasoline, even when running higher boost levels than 23 PSI.
The EF3 is a good choice sure, but I might also take a look at the BBK-B, or the BBK-C even. Don't do any IC smaller than the BR "Race" either.
However, Dave Buschur took issue with me and explained, in a nice way that I was full of myself. He said that based upon his experience, 10:1 is perfectly doable, even on 93 octane pump gasoline, even when running higher boost levels than 23 PSI.
The EF3 is a good choice sure, but I might also take a look at the BBK-B, or the BBK-C even. Don't do any IC smaller than the BR "Race" either.
I dont really have a hp number goal, but if I had to give out a number-- well anything over 400 I'll be smiling.
My goals for my new setup is to improve on what I had. I dont need to rev super high, if I can get away with an 8k rpm or somewhere near that it should work well down the long straight. Ideally I would like to have enough rpm where I can stay in 4th so I dont need to downshift, or at least enough mph where I would be in 5th longer, so Im not upshifting then downshifting 2 seconds later. with the 2.3, I beleive 7800 would do, 8k would be a plus.
The EF3 is a good turbo to match up with this stroker motor. It has potential for the hp I would like. One reason I am not sure I want to tune past 30 psi is I would like to use the Works or Tomei dv. Since they are oem style, they seem to have the best driveability but from reading, seem to not hold more than 29-30 psi. There are dvs out there that can hold more, but from reading seem to have part throttle issues. At a track that isnt a good thing.
Anyhow, enough rambling. Just wanted to give more input as to why Im choosing what Im choosing.
Last edited by TommiM; Jun 11, 2012 at 10:20 AM.
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