(Updated) Does this rear wheel power sound accurate?
12-25-2005, 03:16 AM
#1
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(Updated) Does this rear wheel power sound accurate?
Howdy all,
Just wanted to see if this seemed low to anyone else?
2000 GT convert w/rebuilt 4.6, manley pistons and rods, etc etc, 42lb injectors, etc etc.
Vortech S trim supercharger.
Bassani xpipe and flowmasters.
397 rear wheel horsepower, 386 torque.
I know this isnt super detailed, but am I crazy, or does this seem a bit low? The motor is basically the new cobra motor... I dont know, this horsepower just feels low. I have been told this is the most power I can get out of the car, but I feel like it should be capable of more without hurting anything in the motor?
Just wanted to see if this seemed low to anyone else?
2000 GT convert w/rebuilt 4.6, manley pistons and rods, etc etc, 42lb injectors, etc etc.
Vortech S trim supercharger.
Bassani xpipe and flowmasters.
397 rear wheel horsepower, 386 torque.
I know this isnt super detailed, but am I crazy, or does this seem a bit low? The motor is basically the new cobra motor... I dont know, this horsepower just feels low. I have been told this is the most power I can get out of the car, but I feel like it should be capable of more without hurting anything in the motor?
12-25-2005, 10:13 AM
#3
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RE: Does this rear wheel power sound accurate?
sounds like a conservative tune "The motor is basically the new cobra motor... I dont know, this horsepower just feels low. I have been told this is the most power I can get out of the car, but I feel like it should be capable of more without hurting anything in the motor? "
the motor is a two valve, and judging by what you wrote, its got stock heads and cams so that hp sounds about right for a conservative tune with an s trim. with forged guts you could up the boost, which is probably around 9-12 psi
the motor is a two valve, and judging by what you wrote, its got stock heads and cams so that hp sounds about right for a conservative tune with an s trim. with forged guts you could up the boost, which is probably around 9-12 psi
12-25-2005, 10:50 AM
#4
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RE: Does this rear wheel power sound accurate?
First, more info would help: it helps figure things out to know the RPM for the HP and torque peaks -- that gives a clue about what is going on. Also, did you do anything to the heads, do you have stock cams, and in particular, what is the compresison ratio and the boost you measure at the HP peak?
Regardless, as the motor being able to take more: you put in good aftermarket pistons and rods, but what about the crank? Did you replace it with an aftermarket forged crank? If not dod you have the stock one checked(magnafluxed, trued, etc.), and anything done to it (precision balancing, knife-edging?). I would not worry, though, I think your engine can take this amount of power, or more, all day long.
As to comparison with the new Cobra motor, I assume you mean the 2003-2004 Cobra. You have the same displacement, but unless you went to DOHC heads, you have two valves and one intake and one exhaust port per cylinder while that Cobra has four valves and two intake and two exhaust ports: it breathes better. The Cobra also has a screw-type supercharger, which builds boost earlier in the RPM range than your Vortech. It also has all forged internals but assuming you looked after your crank I think that is about equal with your rebuild.
Still, your engine sounds like a pretty good set up. 397 RWHP is not too shabby and its about what I would expect for this set up "out of the box" -- the first time you get it calibrated and running right. There might be some more there.
First, realize you have a centrfugal supercharger rather than the Cobra's screw type. This difference is important as you move forward. First, centrigual SCs tend to have a more exponential boost vs. RPM curve than screw-type SCs: they produce little boost at low RPM but come on very strong at high RPM. Your engine will never be the torque beast that the Cobra is (if you put a small enough pulley on it to build that much boost down low, and assuming it does not overev itself and break, then it would produce too much boost at high RPM).
Second, and more important to your purpose though, a centrifugal supercharger's design means it is a boost rather than air flow generator (opposite of the screw type's cahracteristics) and that makes it relatively senstive to resistance to air flow in the manifold and heads -- thus, the way to more power on your engine is probably the paying careful attention to intake manifold, heads, and cam. You may discover that going to a smaller pulley does little for you (I'd try it anyway, in small increments - its cheap and it might work), because the intake and heads resist flow. A new, less restrictive intake manifold, heads with some porting, and a bigger cam profile, would probably help. I would think you could get to 450 RWHP here with attention to all this.
Regardless, as the motor being able to take more: you put in good aftermarket pistons and rods, but what about the crank? Did you replace it with an aftermarket forged crank? If not dod you have the stock one checked(magnafluxed, trued, etc.), and anything done to it (precision balancing, knife-edging?). I would not worry, though, I think your engine can take this amount of power, or more, all day long.
As to comparison with the new Cobra motor, I assume you mean the 2003-2004 Cobra. You have the same displacement, but unless you went to DOHC heads, you have two valves and one intake and one exhaust port per cylinder while that Cobra has four valves and two intake and two exhaust ports: it breathes better. The Cobra also has a screw-type supercharger, which builds boost earlier in the RPM range than your Vortech. It also has all forged internals but assuming you looked after your crank I think that is about equal with your rebuild.
Still, your engine sounds like a pretty good set up. 397 RWHP is not too shabby and its about what I would expect for this set up "out of the box" -- the first time you get it calibrated and running right. There might be some more there.
First, realize you have a centrfugal supercharger rather than the Cobra's screw type. This difference is important as you move forward. First, centrigual SCs tend to have a more exponential boost vs. RPM curve than screw-type SCs: they produce little boost at low RPM but come on very strong at high RPM. Your engine will never be the torque beast that the Cobra is (if you put a small enough pulley on it to build that much boost down low, and assuming it does not overev itself and break, then it would produce too much boost at high RPM).
Second, and more important to your purpose though, a centrifugal supercharger's design means it is a boost rather than air flow generator (opposite of the screw type's cahracteristics) and that makes it relatively senstive to resistance to air flow in the manifold and heads -- thus, the way to more power on your engine is probably the paying careful attention to intake manifold, heads, and cam. You may discover that going to a smaller pulley does little for you (I'd try it anyway, in small increments - its cheap and it might work), because the intake and heads resist flow. A new, less restrictive intake manifold, heads with some porting, and a bigger cam profile, would probably help. I would think you could get to 450 RWHP here with attention to all this.
12-25-2005, 01:07 PM
#5
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RE: Does this rear wheel power sound accurate?
Howdy folks!
First off, thanks for the advice; i'll try to fill in as much info as I can...
The crank is a cobra crank... the heads are aftermarket, but I dont know the make
Cam is stock, as is manifold. The compression is, i THINK, 8.7:1? Does that sound right? Boost is about 9 psi at max. I am away from home for the holidays, so dont have all my specifics here... I do have my dyno, tho, and I'll post it when I can figure out why image shack isnt accepting it
I do wish I had a roots style instead of a cent. blower, but what can you do
Okay, let me go see if I can find a way to get my dyno sheet on here to give you a better look. Again, thanks so much, I need all the help I can get
First off, thanks for the advice; i'll try to fill in as much info as I can...
The crank is a cobra crank... the heads are aftermarket, but I dont know the make
Cam is stock, as is manifold. The compression is, i THINK, 8.7:1? Does that sound right? Boost is about 9 psi at max. I am away from home for the holidays, so dont have all my specifics here... I do have my dyno, tho, and I'll post it when I can figure out why image shack isnt accepting it I do wish I had a roots style instead of a cent. blower, but what can you doOkay, let me go see if I can find a way to get my dyno sheet on here to give you a better look. Again, thanks so much, I need all the help I can get
12-25-2005, 02:24 PM
#7
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RE: Does this rear wheel power sound accurate?
At 8psi my dad made 355rwhp on his 2v 01 GT with the saleen blower, so id go get that thing tuned, if you have forged rods and pistons id even get some more boost in there if your fuel system can handle it.
12-25-2005, 02:26 PM
#8
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RE: Does this rear wheel power sound accurate?
ORIGINAL: Shifty101Easy
i dont know a whole lot but for some reason that compression ratio sounds low to me...?
i dont know a whole lot but for some reason that compression ratio sounds low to me...?
One thing on the dyno numbers, what kind of dyno was it? They all come out different. That and it is nothing more than a number, dynos are meant to used as tool for tuning and such, the real number that matters is on your timeslip.
12-25-2005, 02:40 PM
#9
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RE: Does this rear wheel power sound accurate?
*laugh* JD, you sound like my mechanic He always says "Dont worry about the numbers, worry about how the car goes," but I always chalked that up to his not getting a ton of power out of the car
I am trying to get the dyno sheet online but imageshack is acting up... it is a dynojet dyno, not one of those mustang ones or whatever that tend to register low hp.
I am not trying to sound grinchy, but I was just disappointed that a new motor couldn't break into the 400 horsepower. I know that is TOTALLY silly, but... after spending 11 grand, you just feel like you should gain more than 50 horse (the car was at 352 rwhp before I blew the first motor.) At this point I've done the suspension, the wheels and tires, the exhaust, the chip, the gears, the brakes, new motor and new tranny, some fuel system stuff, and a host of little things, and just felt like, after reading stories of 500 hp cars every day, that somehow mine just wasnt reaching its potential.
The fuel system is okay, but the pump might be going (see the appropriate post... I totally just found this forum and so posted a few things here )... I am not sure if it IS going, but...
Anyway, thanks much guys, JD you in particular, I really appreciate the advice. Unfortunately I dont have a cage, so no slips for me... this is purely a stoplight to stoplight car.
He always says "Dont worry about the numbers, worry about how the car goes," but I always chalked that up to his not getting a ton of power out of the carI am trying to get the dyno sheet online but imageshack is acting up... it is a dynojet dyno, not one of those mustang ones or whatever that tend to register low hp.
I am not trying to sound grinchy, but I was just disappointed that a new motor couldn't break into the 400 horsepower. I know that is TOTALLY silly, but... after spending 11 grand, you just feel like you should gain more than 50 horse (the car was at 352 rwhp before I blew the first motor.) At this point I've done the suspension, the wheels and tires, the exhaust, the chip, the gears, the brakes, new motor and new tranny, some fuel system stuff, and a host of little things, and just felt like, after reading stories of 500 hp cars every day, that somehow mine just wasnt reaching its potential.
The fuel system is okay, but the pump might be going (see the appropriate post... I totally just found this forum and so posted a few things here
)... I am not sure if it IS going, but...Anyway, thanks much guys, JD you in particular, I really appreciate the advice. Unfortunately I dont have a cage, so no slips for me... this is purely a stoplight to stoplight car.
12-25-2005, 03:20 PM
#10
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RE: Does this rear wheel power sound accurate?
ORIGINAL: JD1969
He has a blower, therefor wants/needs a lower compression so that he run more boost safely.
One thing on the dyno numbers, what kind of dyno was it? They all come out different. That and it is nothing more than a number, dynos are meant to used as tool for tuning and such, the real number that matters is on your timeslip.
ORIGINAL: Shifty101Easy
i dont know a whole lot but for some reason that compression ratio sounds low to me...?
i dont know a whole lot but for some reason that compression ratio sounds low to me...?
One thing on the dyno numbers, what kind of dyno was it? They all come out different. That and it is nothing more than a number, dynos are meant to used as tool for tuning and such, the real number that matters is on your timeslip.