My 951 mod story...
12-19-2001, 10:23 AM
#31
Race Director
I still cannot understand 300 HP with 8.5psi boost at 6000 RPM and an 8:1 compression engine.
12-19-2001, 09:39 PM
#35
Race Director
Yeah, it used to be at http://home.san.rr.com/myzone but that's offline now. My guess is he took it off because he was going to sell his car and get a 911. But now it appears a lot of the stuff is on the SFR website now.
12-21-2001, 10:52 AM
#36
Intermediate
Join Date: Jun 2001
Location: California
Posts: 25
Likes: 0
Received 0 Likes
on
0 Posts
Restrictions in the intake or exhaust reduce the volumetric efficiency. However, these cars are exceedingly well designed and according to JM have VE's close to unity. I accounted for that in calculating what HP one can make at 8.5psi.
The only other way to increase HP is to rev the motor higher. If you maintain VE at higher rev's by up-camming, you get a linear increase in HP by raising the rev limit.
Compression helps only to the point you get close to the auto-ignition temperature. This is the reason race gas is higher octane.
From at least three reliable vendors, the MAF gains alone are about 15 RWHP and that is due to less restriction. This is becasue at any given RPM you can richen the mixture using an AFPR.
I am waiting for an engine builder to state from his engine dyno he made 300 HP with 8.5 psi boost at 6000 RPM.
I like the MAP system and SDSFI is a wonderful system for the money. However, the power increase from less restriction can only be about that of a MAF.
The only other way to increase HP is to rev the motor higher. If you maintain VE at higher rev's by up-camming, you get a linear increase in HP by raising the rev limit.
Compression helps only to the point you get close to the auto-ignition temperature. This is the reason race gas is higher octane.
From at least three reliable vendors, the MAF gains alone are about 15 RWHP and that is due to less restriction. This is becasue at any given RPM you can richen the mixture using an AFPR.
I am waiting for an engine builder to state from his engine dyno he made 300 HP with 8.5 psi boost at 6000 RPM.
I like the MAP system and SDSFI is a wonderful system for the money. However, the power increase from less restriction can only be about that of a MAF.
12-21-2001, 12:11 PM
#38
Drifting
Join Date: Dec 2001
Location: St. Louis
Posts: 2,058
Likes: 0
Received 0 Likes
on
0 Posts
Hey,
aren't we forgetting the turbo as big as my head?! I'll bet if we put a intake temp sensor in the charged air stream it would be SIGNIFICANTLY decreased now compared to the intake temp of the K26 operating a pressure ratio of say 2.6(.8bar post-AFM to 2.1bar or whatever Rage was running with old turbo) versus 1.6 with bigfat turbo. If the VE of the stock motor is so perfect, than why do all of the professional motor builders significantly modify the head? Lindsay Racing's stageII head flows 50cfm more than stock at a given pressure(28" of water column at .480" valve lift). That means denser air in the cylinder all the way around(I think).
As Rage said, all conjecture will end shortly(too bad!).
aren't we forgetting the turbo as big as my head?! I'll bet if we put a intake temp sensor in the charged air stream it would be SIGNIFICANTLY decreased now compared to the intake temp of the K26 operating a pressure ratio of say 2.6(.8bar post-AFM to 2.1bar or whatever Rage was running with old turbo) versus 1.6 with bigfat turbo. If the VE of the stock motor is so perfect, than why do all of the professional motor builders significantly modify the head? Lindsay Racing's stageII head flows 50cfm more than stock at a given pressure(28" of water column at .480" valve lift). That means denser air in the cylinder all the way around(I think).
As Rage said, all conjecture will end shortly(too bad!).
12-21-2001, 03:04 PM
#39
Race Director
However, these cars are exceedingly well designed and according to JM have VE's close to unity.
That's why guys like Millege or Scott Gomes can get 80.9hp/ltr*bar out of these engines. And that was 5-YEARS ago. His latest engines are getting around 90hp/ltr*bar.
Let's take a look at these engines as an example at 8.5psi (1.59bar):
Another data-point to consider is my own car last June. I got 290rwhp @ 12psi (TurboTim will remember this, he said, "hey, that's pretty good for the boost"). That's at the SAME boost level as a stock 951, but I got about 100rwhp more with just bolt-on mods like an MAF kit and bigger more efficient ball-bearing turbo.
The only other way to increase HP is to rev the motor higher. If you maintain VE at higher rev's by up-camming, you get a linear increase in HP by raising the rev limit.
But a TURBO completely bypasses the 100% displacement limit of the engine. It can cram in more VOLUME (mass) of air than the NA engine can actually hold at 100% VE. No need to rev higher, just turn up the boost and you'll get more power at the SAME rpm as an NA car.
05-23-2002, 02:00 AM
#40
Racer
Join Date: Jun 2001
Location: Santa Cruz, CA
Posts: 429
Likes: 0
Received 0 Likes
on
0 Posts
This board is amazing.
I love getting my interest piqued- tip of the hat to Danno...
...and with a little digging in a free moment discovering this treasure.
Wow.
Rage2, I really need to come up to Canada on the XX and see how your beast does, I need a sdsefi bad. My wife just rolled her eyes tonight when I showed her your dyno videos, so it must be a good idea
Cheers,
I love getting my interest piqued- tip of the hat to Danno...
...and with a little digging in a free moment discovering this treasure.
Wow.
Rage2, I really need to come up to Canada on the XX and see how your beast does, I need a sdsefi bad. My wife just rolled her eyes tonight when I showed her your dyno videos, so it must be a good idea
Cheers,
05-23-2002, 02:44 AM
#41
Three Wheelin'
Thread Starter
Join Date: Sep 2001
Location: Calgary, Alberta, Canada
Posts: 1,596
Likes: 0
Received 0 Likes
on
0 Posts
[quote]Originally posted by Steve Cooper:
<strong>Rage2, I really need to come up to Canada on the XX and see how your beast does, I need a sdsefi bad. My wife just rolled her eyes tonight when I showed her your dyno videos, so it must be a good idea </strong><hr></blockquote>
Anytime. We're allowed passengers for drag strip runs now =).
<strong>Rage2, I really need to come up to Canada on the XX and see how your beast does, I need a sdsefi bad. My wife just rolled her eyes tonight when I showed her your dyno videos, so it must be a good idea
</strong><hr></blockquote>Anytime. We're allowed passengers for drag strip runs now =).
