SBR 2.3 GT35R Dyno results
Apr 1, 2005 | 12:10 PM
#76
You are not going to shift your peak VE by 3K rpm unless there are drastic changes. I don't consider going .020" over on the bore drastic. Nor does increasing stroke, decreasing rod ratio raise peak VE. I don't think you understand what I'm saying...
By drastic I would say, change port length in the head, change the port angles by 20-30 degrees, drastically change port shape, reduce stroke from 88mm, to 78mm, increase bore by 3-4mm, unshroud the valves, Develop a tuned intake & exh. manifold for the engine combo that you are running. HKS cams and other pupular turbo cams are not drastic cams, they are rather conservative because that what typical turbo engine like! If you are building a 12K rpm motor you would need to impliment these drastic changes, then you would move your peak torque, thus VE point drastically higher, which will in turn raise your peak HP point in the RPM range.
I'm not trying to arue, just stating what I've learned over the years.
Just for reference.....
On a well built 2.3L with a GT35R and HKS 272 cams, you will get about 20pis at about 3500 rpm on the street in 3rd gear, depending on what turbine housing you are using.
I've looked at logs on the EMS and where the boost peaks, that's where you wind up with peak torque, it then usually levels off, then of course drop as rpm's increase and VE goes down.
By drastic I would say, change port length in the head, change the port angles by 20-30 degrees, drastically change port shape, reduce stroke from 88mm, to 78mm, increase bore by 3-4mm, unshroud the valves, Develop a tuned intake & exh. manifold for the engine combo that you are running. HKS cams and other pupular turbo cams are not drastic cams, they are rather conservative because that what typical turbo engine like! If you are building a 12K rpm motor you would need to impliment these drastic changes, then you would move your peak torque, thus VE point drastically higher, which will in turn raise your peak HP point in the RPM range.
I'm not trying to arue, just stating what I've learned over the years.
Just for reference.....
On a well built 2.3L with a GT35R and HKS 272 cams, you will get about 20pis at about 3500 rpm on the street in 3rd gear, depending on what turbine housing you are using.
I've looked at logs on the EMS and where the boost peaks, that's where you wind up with peak torque, it then usually levels off, then of course drop as rpm's increase and VE goes down.
Apr 1, 2005 | 12:17 PM
#77
VE at the most will change by 10%, and that is at the most. your looking at a 50% decrease in torque from a stock car at 3500 rpm. if your at peak boost, there is something VERY wrong and no, VE will not account for this difference. or else if you look at it in RPM standpoint, you have shifted the torque band to the right by around 40% VE makes a difference, but again, not that big of a difference. It is very easy to look at your dyno graph and see your not making peak boost until 4500-5000 rpm.
THANK YOU MARTIN! always good to hear someone that agrees with me. at least that means i haven't fallen off the deep end (yet...)
THANK YOU MARTIN! always good to hear someone that agrees with me. at least that means i haven't fallen off the deep end (yet...)
Apr 1, 2005 | 12:21 PM
#78
thats also something that plays a big factor in this that i don't think we have touch on. it is the exhaust turbine. the housings and turbine sizes can play a huge part in where you make your power.
Apr 1, 2005 | 05:44 PM
#80
Originally Posted by KevinD
i know that head design and stroke have a lot to do with torque. the neat thing about the stroker crank is not only does it increase displacement slightly, but having longer throws on the crank itself inherantly increase torque (longer moment arm, thus more torque). i thought i mentioned the intake manifold properties, as well as headwork, and valve lift. but on our cars because all of this stuff is constant, long stroke characteristics don't make a difference at high RPM's or low RPM's. it works the same way at both levels (which is a good thing). the head work and air flow design properties also make a difference but no so much that it would push your torque curve over by 2000rpm. ideally, your only going to gain a tiny bit of power from designing manifolds for high RPM's so on a torque curve you will see the torque increase as the boost increases, until the boost reaches what it was set at, then the torque curve will fluctuate minimally, and increase slightly as the engine speeds increase provided your holding boost steady. the best torque curve will remain flat all through the rpm band, showing that flow properties are ideal for all RPM ranges.
keith, what boost levels are you using, what sized turbo, and where did your boost level reach set pressure at? i bet it is a lot closer then 2000 rpm (and i would bet within 500rpm), and if you use my following formula, i bet it is within 100rpm.
i think we need to coin a new term for engine dyno graphs. we will call it the torque rise time. this will be where the torque has increased to within 10% of peak. for the cobra plot i posted, his rise time was the instant they started the dyno, or about 2000 rpm. even though the torque increases slightly, he is within 10% throughout the entire run. for this 550hp monster, i'll give him 455ftlb of torque max*.9 = 410 ftlb, at 4800 rpm. i will call this his rise time, which is where he is just maxing max boost. he is not making max boost at 3500 rpm because he is only making 160 ftlb of torque there, and if head work along makes a 200% increase in power over 1500 rpm, then you should get a job with ferrari F1.
keith, what boost levels are you using, what sized turbo, and where did your boost level reach set pressure at? i bet it is a lot closer then 2000 rpm (and i would bet within 500rpm), and if you use my following formula, i bet it is within 100rpm.
i think we need to coin a new term for engine dyno graphs. we will call it the torque rise time. this will be where the torque has increased to within 10% of peak. for the cobra plot i posted, his rise time was the instant they started the dyno, or about 2000 rpm. even though the torque increases slightly, he is within 10% throughout the entire run. for this 550hp monster, i'll give him 455ftlb of torque max*.9 = 410 ftlb, at 4800 rpm. i will call this his rise time, which is where he is just maxing max boost. he is not making max boost at 3500 rpm because he is only making 160 ftlb of torque there, and if head work along makes a 200% increase in power over 1500 rpm, then you should get a job with ferrari F1.
What you are not taking into account is that even with ZERO boost a Mitsubishi 4g63 engine doesn't have a flat torque curve. Due to compromises in head design, cams, intake manifold etc we have a torque curve that rises, peaks, and then falls. All of this is determined by the design of the engine, and adding boost pressure to the equation just magnifies the torque in EVERY area.... so you get a rise, peak, and fall in torque even if you had a supercharger setup instead of a turbo setup.
Later,
Keith
Thread
Thread Starter
Forum
Replies
Last Post
SBR INC
Vendor Announcements
85
Nov 26, 2016 08:39 AM
SBR INC
Evo Vendor 'Group Buy / Specials' Classifieds
22
Jul 27, 2010 12:33 PM
SBR INC
Evo Vendor 'Group Buy / Specials' Classifieds
1
Mar 18, 2010 10:19 AM
SBR INC
Evo Vendor 'Group Buy / Specials' Classifieds
1
Dec 23, 2009 03:33 PM
SBR INC
Evo 'For Sale' External Engine / Power
53
Feb 9, 2009 02:41 PM
