Boosted 4V cobra motor vs Ls1
01-29-2007, 08:45 PM
#21
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i agree a 427 lsx motor at 12 psi making 500/500... man something is WAY off there... my little lt1 355's one blower and one turbo did over 500 on 12 psi.. somehting is outta whck there on that!
Chris
Chris
01-29-2007, 09:05 PM
#22
Originally Posted by 96silverram
What is the Nasty little secret on the 4V heads from 96 - 98 cobra's ? 
01-29-2007, 09:08 PM
#23
Originally Posted by lcvette
i agree a 427 lsx motor at 12 psi making 500/500... man something is WAY off there... my little lt1 355's one blower and one turbo did over 500 on 12 psi.. somehting is outta whck there on that!
Chris
Chris
01-29-2007, 09:13 PM
#25
Originally Posted by 52172
heads flow 299@ .600 and 307@.650
Last edited by 6techniques; 01-29-2007 at 09:19 PM.
01-29-2007, 09:57 PM
#26
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Originally Posted by lcvette
"edi
I think this will be a VERY interesting power build off.. I don't know which side of the fence I would hang my flag, obviously I am a GM man but I do think that his motor is going to be able to handle around 21+ psi on pump gas and a good tune with some moderate timing.. an LS1 is not gonna handle that kind of pressure on pump gas. so you may hit your detonation threshold long before him while he is continually able to turn the boost up.
Chris
I think this will be a VERY interesting power build off.. I don't know which side of the fence I would hang my flag, obviously I am a GM man but I do think that his motor is going to be able to handle around 21+ psi on pump gas and a good tune with some moderate timing.. an LS1 is not gonna handle that kind of pressure on pump gas. so you may hit your detonation threshold long before him while he is continually able to turn the boost up.
Chris
Just because cobra's can run 21+psi and an ls1 wont on pump gas has nothing to do with how much air the turbos are flowing... PSI is just a measure of force excerted on an area... I think that a 76 would be a lil big for that motor.... I know it'll work...
01-29-2007, 10:30 PM
#27
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Smearin,
I am 100% completely aware of the difference of boost pressure and actual flow as I do alot of work in the field
, however I think alot of people here also overlook the fact thjat even though boost gauge pressure is a measure of restriction, it is also the pressure at the back of the intake valve and while in alot of cases boost pressure may not be viewed as ideal.. on smaller cube motors with good flowing heads and intake, it may not always be a restriction in the intake tract but the top of the piston and the pressure differential across the cylinder and the intake port... after all the more pressure the higher velocity and the greate amount of airflow will be forced through a restrcitive port albeit at a higher temperature because nothing escaped physics and the laws of compressed gas and the direct relation to pressure and heat.
if you look at a supra, its a 187 cubic inch engine and it may show upwards of 35 pounds of boost in extensive builds.... does that mean that just because it pushes 35psi that it won't make the power? NO, in fact power per pound of boost may not be as efficient at higher level but it will STILL show a gain in power, so do not underestimate the power of pressure just because it is not the most IDEAL setup.
and I am in no way trying to compare your car to another but I think your turbo is small for your motor.. but then again I like the feel of a larger turbo and more top end rather then instantaneous throttle response.. so turbo sizing is kinda like clothes.. different sized turbos will created two very different types of power band.. it just is what you wanna drive. I have ridden in a few 76mm 03-04 cobra cars and gotta say that I think the 76mm unit is Sized spot on for the power range and rpm band they have with the 4 valves per cylinder and and DOHC's. hell they jump straight into the F1A blower in most cases and the blowers work very well on them. if you look at the compressor map of a 76mm unit, you will see that those efficiency islands rise upwards against the pressure ratio on the left hand side so they stay efficient when pushing up in the high boost range, some may even tell you that they find their 'happy spot" where they really begin producing airflow efficiently at their max pressure ratio and max airflow which on the cobra motors happens pretty high up in the rev range where they are capable of moving airflow like an bigger motor at lower rpm.
in no way am I trying to pick a fight, but I see too many people go straight to the "boost pressure is a bad thing" and while the restriction is clearly just that.. more pressure does not mean you get less gain, just that you are having to push harder for that gain. in the end.. 20+ pounds of boost is gonna make air get where it needs to be.. on top of the piston in the intake stroke!
Chris
I am 100% completely aware of the difference of boost pressure and actual flow as I do alot of work in the field
, however I think alot of people here also overlook the fact thjat even though boost gauge pressure is a measure of restriction, it is also the pressure at the back of the intake valve and while in alot of cases boost pressure may not be viewed as ideal.. on smaller cube motors with good flowing heads and intake, it may not always be a restriction in the intake tract but the top of the piston and the pressure differential across the cylinder and the intake port... after all the more pressure the higher velocity and the greate amount of airflow will be forced through a restrcitive port albeit at a higher temperature because nothing escaped physics and the laws of compressed gas and the direct relation to pressure and heat.if you look at a supra, its a 187 cubic inch engine and it may show upwards of 35 pounds of boost in extensive builds.... does that mean that just because it pushes 35psi that it won't make the power? NO, in fact power per pound of boost may not be as efficient at higher level but it will STILL show a gain in power, so do not underestimate the power of pressure just because it is not the most IDEAL setup.
and I am in no way trying to compare your car to another but I think your turbo is small for your motor.. but then again I like the feel of a larger turbo and more top end rather then instantaneous throttle response.. so turbo sizing is kinda like clothes.. different sized turbos will created two very different types of power band.. it just is what you wanna drive. I have ridden in a few 76mm 03-04 cobra cars and gotta say that I think the 76mm unit is Sized spot on for the power range and rpm band they have with the 4 valves per cylinder and and DOHC's. hell they jump straight into the F1A blower in most cases and the blowers work very well on them. if you look at the compressor map of a 76mm unit, you will see that those efficiency islands rise upwards against the pressure ratio on the left hand side so they stay efficient when pushing up in the high boost range, some may even tell you that they find their 'happy spot" where they really begin producing airflow efficiently at their max pressure ratio and max airflow which on the cobra motors happens pretty high up in the rev range where they are capable of moving airflow like an bigger motor at lower rpm.
in no way am I trying to pick a fight, but I see too many people go straight to the "boost pressure is a bad thing" and while the restriction is clearly just that.. more pressure does not mean you get less gain, just that you are having to push harder for that gain. in the end.. 20+ pounds of boost is gonna make air get where it needs to be.. on top of the piston in the intake stroke!
Chris
01-30-2007, 11:38 AM
#28
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Originally Posted by Smearin
I think that a 76 would be a lil big for that motor.... I know it'll work...
As far as the poster goes, if your bother has a good kit (tubular headers , well designed) you could be in trouble.
I helped one of my friends install a PTS kit with a 76GTS turbo on his 96 cobra. The motor only had forged rods and pistons (stock cams, heads intake) which dropped the compression to around 8.7-8.9.
He put on 60lb injectors, spec III clutch, a couple of fuel pumps and a good tune. He dynoed @540 rwhp at 10psi but drove around at 14psi using pump gas (93 oct). His car had full boost by 3800-3900 rmps
The cobra was faster at 10psi than mine (I was running 10 psi with a TTI street kit), at 14psi, he killed me!!!
The dumbass ended up selling the car to a guy who put on a set of sticky tires, dumped some race gas in and turned the boost to 19psi and ran 10.20’s at 139 mph!!!. The guy then changed gears (went to 373’s) and bumped to boost to 21 and went 9.90’s at 143mph. This was all with the 1996 stock heads, cams and intake.
Either way, the one with the most $ will prevail, I just think it costs a little more for an ls1 to get there. If y’all run the same boost, you will probably beat him (being that your kit is better than mine), but I think he will be able to run more boost on pump than you, which will probably swing the advantage his way.
Should be some great races!! Definitely post the circumstances and outcomes!!
Good luck!
01-30-2007, 11:51 AM
#29
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Originally Posted by SS4Matt
the cobra has a ton less valvetrain weight and will be able to rev way higher then an LS1
i'm not sure about turbo's, but a few weeks ago there was a C5R block 427 corvette at my buddys shop with a vortech T-trim blower on it that was a manual and put down like 500/500 somewhere around there, i forget the exacts. anyways, then my buddy's '98 cobra was on the rollers next, it has been swapped to an auto, it's a stroker 5.1ish motor with custom cams and dished pistons around 8.5 cr. it also had a vortech T-trim blower and through his auto it put down 570hp and i forget the torque, but being a smaller motor with the same blower and through an unlocked auto, the cobra was spinning a lot higher and making a lot more power. given the vette was running like 12 psi, and the cobra was pushing 25psi if memory serves me
i would have to say there's way too many variables,
it all comes down to the golden rule...he with the most gold rules!
i'm not sure about turbo's, but a few weeks ago there was a C5R block 427 corvette at my buddys shop with a vortech T-trim blower on it that was a manual and put down like 500/500 somewhere around there, i forget the exacts. anyways, then my buddy's '98 cobra was on the rollers next, it has been swapped to an auto, it's a stroker 5.1ish motor with custom cams and dished pistons around 8.5 cr. it also had a vortech T-trim blower and through his auto it put down 570hp and i forget the torque, but being a smaller motor with the same blower and through an unlocked auto, the cobra was spinning a lot higher and making a lot more power. given the vette was running like 12 psi, and the cobra was pushing 25psi if memory serves me
i would have to say there's way too many variables,
it all comes down to the golden rule...he with the most gold rules!
Matt,
The Cobra made 574hp at 6550 and 470tq at 6050. It was 20psi on the dyno but makes 22-23 on the street. Just had to correct you.
01-30-2007, 11:52 AM
#30
Well he is running the wrong gear I believe he has 4:10, but he put in a viper spec T-56. We both will run as much boost as we can using the same gas and same turbo. I will keep everyone posted on the outcome. I think I will hit full boost much earlier since my Ls1 will spool the turbo faster which should give me a great advantage. My topend is not too shabby with my fully hand ported heads with 2.02 1.6 valves and an aftermarket cam. Plus I call my SS the Snake Slayer aka cobra eater.
01-30-2007, 11:54 AM
#31
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Originally Posted by 52172
wanna bet?
01-30-2007, 12:22 PM
#33
Originally Posted by slow trap
if i had a c5r 427 at 12 psi and could only muster 500/500 i would be very,very dissapointed 
back to the poster, i think you will have the most "useable" power.
back to the poster, i think you will have the most "useable" power.
Yea same here...c5r 427 at 12 psi making 500/500? Def something wrong if thats all the power he could put down...
01-30-2007, 12:28 PM
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Cubes really dont matter when both cars are turbocharged. Head design,compression ratio,etc... all play a factor in determing how much flow goes into the motor. Take a look at the new K20 out of the RSX. Those cars make nearly 400rwhp at 11psi. I dont recall any B18 at those psi levels even coming close to that, eventhough they use the same displacement. Or take a look at the BMW M3. HPF(horsepowerfreaks.com) made almost 700rwhp at 13psi on a completely stock motor.
01-30-2007, 12:37 PM
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I love to run higher compression. My last setup was at 10:1(mr2) and my 350z is at 9:5:1. Makes the car more responsive and helps the turbo spool slightly faster. Plus you make more power with less boost!
01-30-2007, 12:38 PM
#38
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you should start with an LQ4 cast iron block, make it a forged 408 stroker with ported L92 heads and single plane intake 
if you have to stay stock cubed i think it would be close.. that motor is literaly built for boost (thats the only possible way Ford can make hp with mod motors) LSx really isnt built for boost, but with turbos and such they can produce massive hp. get something like a vic jr intake, itll help you out a lot.
if you have to stay stock cubed i think it would be close.. that motor is literaly built for boost (thats the only possible way Ford can make hp with mod motors) LSx really isnt built for boost, but with turbos and such they can produce massive hp. get something like a vic jr intake, itll help you out a lot.
01-30-2007, 01:09 PM
#40
Thats what I am hoping. I don't want to spend any more money so I am sticking with the ls6 intake. Might make more power under the curve anyway and aid in taking him. I will definitly spool the turbo faster which I think my power under the curve will be all that it will take to smoke his ***. I even doubt he will make more power up top, but we need to see that.
I am hoping to be able to push 14lbs of boost with the 9.8:1 compression, but we will also have too see about that. 14 lbs should put me around 650rwhp I am guessing. We are gonna spend a lot of time on the tune that is for sure I have already stressed that with my builder.
I am hoping to be able to push 14lbs of boost with the 9.8:1 compression, but we will also have too see about that. 14 lbs should put me around 650rwhp I am guessing. We are gonna spend a lot of time on the tune that is for sure I have already stressed that with my builder.