Thoughts on Comptech vs. Speedcraft
08-28-2002, 09:32 PM
#1
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Thoughts on Comptech vs. Speedcraft
-- Disclaimer-- This thread is not initiated to discuss which is better, worse, cheaper, more expensive, more driveable, etc. Both kits work as advertised. I only want to discuss some critical differences in performance and the components of the kits that may create those differences.
O.k.,
I've tested the Speedcraft and the Comptech kit extensively on the dyno. And while I've only dyno'd one Speedcraft, I've seen enough dyno sheets from elsewhere to know what they do.
In every case, the basics of the comparison are the same. The centrifugal supercharger of the Comptech takes a while to get going, and makes its peak boost and peak power right at the redline. The Speedcraft turbo starts making some serious thump by 4000 rpm and carries a big torque plateau right through 8000 rpm.
What always bothered me a bit was that, when both kits are tuned, the non-intercooled Comptech kit seems to produce equal or better top end power at equal or lower boost pressures vs. the Speedcraft. I asked myself "why?". Myself responded..:-)
But seriously, why? So I decided to look at the compressor map for the T04B 60-1 on the Speedcraft and the Paxton Novi1000 on the Comptech kit. I would have preferred a real compressor map for the Novi, but couldn't find one. However, in looking at the T04B map, I noticed that at the power levels (330-350 crank hp) and pressure ratios (1.4-1.5) the Speedcraft kit runs at, the turbo is kind of on the edge of its compressor map, moving out into the 70-73% efficiency range (vs. the 78% max efficiency area). It looks like this turbo would really like to be on a somewhat less efficient and/or smaller engine with a higher pressure ratio. Oh, and the maximum mass air flow the turbo will support is 65 lbs/min.
By comparison, all we know about the Novi is that it is good for 850 CFM. That doesn't tell us a whole lot, but if it can flow anywhere near that amount with a pressure ratio of 1.5-2, it'll be good for 100 lbs/min of mass air flow. The Novi also appears to be designed to run in the 7-10 psi range, or a pressure ratio of 1.5-1.7. This is about the same as the T04B 60-1. But perhaps the Novi runs more efficiently in the critical range?
<speculation mode on>
Might the Novi be better sized for maximum power than the T04B 60-1 when we're talking about the power levels and pressure ratios that we deal with on the F20C? The T04B 60-1 looks like it would work really well at about 12 psi of boost and 400 crank hp on the S2000 (which is a numbers combo that is legit with lower compression). But at the lower boost levels, the drop in efficiency from being on the edge of the map could account for the reduced top end relative to the Novi1000 (when corrected for boost, intake temp, etc.).
<speculation mode off>
Interesting stuff. If anyone has a compressor map for a Novi1000, please let me know.
UL
O.k.,
I've tested the Speedcraft and the Comptech kit extensively on the dyno. And while I've only dyno'd one Speedcraft, I've seen enough dyno sheets from elsewhere to know what they do.
In every case, the basics of the comparison are the same. The centrifugal supercharger of the Comptech takes a while to get going, and makes its peak boost and peak power right at the redline. The Speedcraft turbo starts making some serious thump by 4000 rpm and carries a big torque plateau right through 8000 rpm.
What always bothered me a bit was that, when both kits are tuned, the non-intercooled Comptech kit seems to produce equal or better top end power at equal or lower boost pressures vs. the Speedcraft. I asked myself "why?". Myself responded..:-)
But seriously, why? So I decided to look at the compressor map for the T04B 60-1 on the Speedcraft and the Paxton Novi1000 on the Comptech kit. I would have preferred a real compressor map for the Novi, but couldn't find one. However, in looking at the T04B map, I noticed that at the power levels (330-350 crank hp) and pressure ratios (1.4-1.5) the Speedcraft kit runs at, the turbo is kind of on the edge of its compressor map, moving out into the 70-73% efficiency range (vs. the 78% max efficiency area). It looks like this turbo would really like to be on a somewhat less efficient and/or smaller engine with a higher pressure ratio. Oh, and the maximum mass air flow the turbo will support is 65 lbs/min.
By comparison, all we know about the Novi is that it is good for 850 CFM. That doesn't tell us a whole lot, but if it can flow anywhere near that amount with a pressure ratio of 1.5-2, it'll be good for 100 lbs/min of mass air flow. The Novi also appears to be designed to run in the 7-10 psi range, or a pressure ratio of 1.5-1.7. This is about the same as the T04B 60-1. But perhaps the Novi runs more efficiently in the critical range?
<speculation mode on>
Might the Novi be better sized for maximum power than the T04B 60-1 when we're talking about the power levels and pressure ratios that we deal with on the F20C? The T04B 60-1 looks like it would work really well at about 12 psi of boost and 400 crank hp on the S2000 (which is a numbers combo that is legit with lower compression). But at the lower boost levels, the drop in efficiency from being on the edge of the map could account for the reduced top end relative to the Novi1000 (when corrected for boost, intake temp, etc.).
<speculation mode off>
Interesting stuff. If anyone has a compressor map for a Novi1000, please let me know.
UL
08-28-2002, 09:57 PM
#2
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Did some more thinking. If the 60-1 wasn't in its ideal operating range, was there a better turbo out there? I looked through Turbonetics catalog and really couldn't find any. Something like a T-76 might be more efficient, but it would spool so much slower that it would negate much of the midrange that the Speedcraft kit provides.
It just appears that with a high revving, high output engine like the F20C, you really can't find an ideal turbo for low boost applications (at least not from Turbonetics). As you bring up the pressure ratios, as I originally mentioned, the 60-1 looks great, but at 6-8 psi you're not getting the best from the turbo. With the big Novi1000, you probably have something that produces a map more like the T-76, but it's not gonna spool (or provide low end) anyways because of the centrifugal belt drive setup, so low end response isn't a big deal.
UL
It just appears that with a high revving, high output engine like the F20C, you really can't find an ideal turbo for low boost applications (at least not from Turbonetics). As you bring up the pressure ratios, as I originally mentioned, the 60-1 looks great, but at 6-8 psi you're not getting the best from the turbo. With the big Novi1000, you probably have something that produces a map more like the T-76, but it's not gonna spool (or provide low end) anyways because of the centrifugal belt drive setup, so low end response isn't a big deal.
UL
08-28-2002, 10:33 PM
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The Novi's just simply huge. That's my conclusion 
.
But your explanation is very clear and should (hopefully) give people an idea of why the Comptech SCs are getting better peak HP.
.But your explanation is very clear and should (hopefully) give people an idea of why the Comptech SCs are getting better peak HP.
08-28-2002, 10:48 PM
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in my opinion, there are two design flaws with the SpeedCraft kit (with one not being SpeedCrafts fault).
i feel the turbo manifold could be greatly improved upon. if you have even seen a turbo manifold for a single turbo Supra...THATS what a manifold should look like. there is a LOT to be gained in boost response, torque, and peak hp from the manifold alone. i also feel the placement of the wastegate causes access stress on the #2-3 cylinders. once again, see a GReddy, HKS, PHR, or SP manifold for a Supra, and you will see optimal placement.
second, i feel with an improved manifold, a larger/better turbo could be used. also, even disregarding the manifold, i feel a larger turbo than the 60-1 unit included in the kit could be used to take advantage of the S2000s 9000 redline. if you look at modded Supra/RX-7/300Z/Grand National dyno sheets, youll see that their full boost RPM is related to their redline by a percentage. for example, if an engine were to redline at 8000, and full boost were to be made at 3500, that is almost 44%. normally, this is considered "good" spool-up for a moderately sized turbo. with a higher redline, and a faster revving engine, you could use a larger turbo that will spool a bit slower, say FB at 4000, but that is the same %age as a quicker spooling turbo on an engine with a lower redline.
get what im sayin?
i feel the turbo manifold could be greatly improved upon. if you have even seen a turbo manifold for a single turbo Supra...THATS what a manifold should look like. there is a LOT to be gained in boost response, torque, and peak hp from the manifold alone. i also feel the placement of the wastegate causes access stress on the #2-3 cylinders. once again, see a GReddy, HKS, PHR, or SP manifold for a Supra, and you will see optimal placement.
second, i feel with an improved manifold, a larger/better turbo could be used. also, even disregarding the manifold, i feel a larger turbo than the 60-1 unit included in the kit could be used to take advantage of the S2000s 9000 redline. if you look at modded Supra/RX-7/300Z/Grand National dyno sheets, youll see that their full boost RPM is related to their redline by a percentage. for example, if an engine were to redline at 8000, and full boost were to be made at 3500, that is almost 44%. normally, this is considered "good" spool-up for a moderately sized turbo. with a higher redline, and a faster revving engine, you could use a larger turbo that will spool a bit slower, say FB at 4000, but that is the same %age as a quicker spooling turbo on an engine with a lower redline.
get what im sayin?
08-28-2002, 10:49 PM
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BTW, all this talk about "turbo-lag" with the supercharged guys...stuff a turbo big enough into the S2000s engine bay to hit full boost at redline and ONLY at redline (just like the supercharger), and you are making 600+ RWHP.
08-28-2002, 10:57 PM
#6
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I'm pretty sure Speedcraft chose the 60-1 in order to bring up the midrange torque curve of the F20C. For a street kit, I'd much rather spool up sooner and get a big midrange hit while sacrificing 10-20 hp up top. Not that the 60-1 doesn't take a bit to spool anyways.
For a race kit, the T-76 looks to have a more appropriate compressor map and would certainly support more hp (a lot more) as long as you didn't mind not making full boost until 4500-5000 rpm.
UL
[QUOTE]Originally posted by JoeD
[B]
second, i feel with an improved manifold, a larger/better turbo could be used. also, even disregarding the manifold, i feel a larger turbo than the 60-1 unit included in the kit could be used to take advantage of the S2000s 9000 redline.
For a race kit, the T-76 looks to have a more appropriate compressor map and would certainly support more hp (a lot more) as long as you didn't mind not making full boost until 4500-5000 rpm.
UL
[QUOTE]Originally posted by JoeD
[B]
second, i feel with an improved manifold, a larger/better turbo could be used. also, even disregarding the manifold, i feel a larger turbo than the 60-1 unit included in the kit could be used to take advantage of the S2000s 9000 redline.
08-28-2002, 11:05 PM
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UL, can you post (or post links to) the compressor map and whatever you have for the Novi?
Does anyone have a compressor map for a whipple or roots charger?
And my main question I think might provide some interesting discussion: How would a twin turbo setup work on this engine? How would you optimally set it up? Sequentially or not?
Blake
Does anyone have a compressor map for a whipple or roots charger?
And my main question I think might provide some interesting discussion: How would a twin turbo setup work on this engine? How would you optimally set it up? Sequentially or not?
Blake
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08-29-2002, 03:30 AM
#8
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UL, we've seen you contribute countlessly on threads pertaining to superchargers and turbos... but to start your own thread inquiring about boost theory?? Besides the academics, could there be another reason? Like maybe researching for building your own kit? <rumour mill starts cranking...>
08-29-2002, 04:01 AM
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UL (and others),
We had looked at another turbo when we starting getting things together for my car... primarily because the guys at Turbonetics were way behind and weren't really giving me a warm fuzzy. I had spoken with some shop in Daytona Beach who primarily upgrade turbo Porsches and they were trying to talk me into going with some twin ball bearing GT25 or GT30 I believe. I'm not sure but I believe it's a Garrett turbo... it was considerably more which would not have mattered to me for the most part but I had already paid for the 60-1 and Dwight didn't think it was worth the extra money. He said he had some bad experiences with the Garrett turbos I believe.
JoeD,
What exactly do you mean by a 'better' manifold. If you're talking about a tubular style.... they can do that. Initially on my car that's all we were doing but we were a little rushed to get the car ready for NOPI and the log style takes ALOT less time. After careful consideration Dwight determined that the extra 30 hours or so that it took him to do the tubular vs. the log style could not justify the cost difference vs. the horsepower gains.
We had looked at another turbo when we starting getting things together for my car... primarily because the guys at Turbonetics were way behind and weren't really giving me a warm fuzzy. I had spoken with some shop in Daytona Beach who primarily upgrade turbo Porsches and they were trying to talk me into going with some twin ball bearing GT25 or GT30 I believe. I'm not sure but I believe it's a Garrett turbo... it was considerably more which would not have mattered to me for the most part but I had already paid for the 60-1 and Dwight didn't think it was worth the extra money. He said he had some bad experiences with the Garrett turbos I believe.
JoeD,
What exactly do you mean by a 'better' manifold. If you're talking about a tubular style.... they can do that. Initially on my car that's all we were doing but we were a little rushed to get the car ready for NOPI and the log style takes ALOT less time. After careful consideration Dwight determined that the extra 30 hours or so that it took him to do the tubular vs. the log style could not justify the cost difference vs. the horsepower gains.
08-29-2002, 07:44 AM
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smcurry, the short answer is - no. I have no interest in developing a turbo kit. However, if some company came to me asking for help in development I'd do it (this has not happened either, so no rumors there).
infinitebass, the maps can be found in the following document (its kind of big):
http://www.binaryjungle.com/pdfs/Turbonetics2002.pdf
derryck and joed, while I'm sure there might be a better turbo and/or manifold out there, for a street kit with a little upside potential, I think the current speedcraft setup does a good job of balancing price and performance.
UL
infinitebass, the maps can be found in the following document (its kind of big):
http://www.binaryjungle.com/pdfs/Turbonetics2002.pdf
derryck and joed, while I'm sure there might be a better turbo and/or manifold out there, for a street kit with a little upside potential, I think the current speedcraft setup does a good job of balancing price and performance.
UL