Author Topic: HELP....my so called performance slug (Read 22841 times)

daniel42au · « **Reply #60 on:** August 12, 2006, 06:13:04 PM »

In respect to your concerns about power output .... Without wanting to be too controversial... what is important to you, horsepower or torque?

I have a 87 Convertible and a 94 Convertible ... the 87 puts out about 240 hp and 330 ft/lb of torque and the 94 puts out 300hp and 330 ft/lbs of torque...interesting huh....

the important part is when then produce those figures...

I got the 87 dyna'ed and to my surprise .... it turned up about 160 rwhp....as you would expect from an instrument which measures output via the rear wheels....but GM measures from the flywheel( and hence the 240hp).... but the plot thickens....because GM doesnt take into account accessories hanging off the engine.

Numbers... numbers.... numbers.... they are unimportant.... because what is important is what happens at the lights!

BOTH cars go 0-60mph in about 6 secs!! even though there is a 60 hp difference.

BECAUSE the thing which gets you mobile from a standing position is TORQUE..... which is the ability of your engine to TWIST around the rear wheels thru the drive shaft, gearbox and diff( which are both geared)....

In the 87 that torque is max'ed in the 3000-4000 rpm range... whilst the max hp comes on line about 5200-5500 range....

So I ask the question... to more knowledgable forum members....

which is more useable Torque or Horsepower?

and where?
at the traffic lights... where 95% of us drive?
or the drag strip ... where 5% of us drive?

cYa

daniel42au
http://members.ozemail.com.au/~daniel42au/

87Z51 · « **Reply #61 on:** August 13, 2006, 06:02:44 PM »

which is more useable Torque or Horsepower?

and where?
at the traffic lights... where 95% of us drive?
or the drag strip ... where 5% of us drive?

Same situation either place.The torque is what gets you moving.
A L98 will out run a LT1 to 60mph on torque alone then
two things happen ;
the L98 with it's TPI intake runs out of breath and the LT1 with it's top end manifold comes on line.
Stock for stock a LT1 will run a faster time than a L98 but the L98 will probably run a better 60Ft.

Inherent problem for L98 cars is the torque is so big low down that traction becomes a problem especially in manual cars.
One of the few situations where it is benefical to bleed off some bottom torque so as not to spin up.

69 DIRTY RAT · « **Reply #62 on:** August 13, 2006, 09:47:43 PM »

Ok This brings me to a Question I've been wanting to know for a while.....When Racing either at the drags or on the track, IS it better to change gears at the highest torque or highest horsepower? to get the fastest out of the car?

MADVET · « **Reply #63 on:** August 14, 2006, 01:39:32 AM »

General rule of thumb is to shift at max HP so the engine revs will fall on to your peak TQ.
Repeat as necessary until you win the race....(or run out of gears);--;46

69 DIRTY RAT · « **Reply #64 on:** August 14, 2006, 03:45:59 PM »

Thanks, that makes sense!

daniel42au · « **Reply #65 on:** August 14, 2006, 08:05:30 PM »

Realising the forumula for converting hp to kw and visa versa is:

Horse power (hp) ---> Kilowatts (kW): hp x 0.7457 = kW
Kilowatts (kW) ---> Horse power (hp): kW x 1.341 = hp

According to your dyno tuner, your car is puting out 182 hp at the rear wheels...

Chevrolet say your car was worth 240 hp at the flywheel when it left the factory 18 years ago... and this is probably without accessories....

The pundits say ya lose about 25% of power from engine to rear wheels.... due to gears, differential, accessories and such....

25% off 240 gives you 60hp... which leaves you with 180 hp.... hmmm....

Also, realise that your local dyno is an experiment of ONE... it may or may not be totally accurate.... it is like the set of scales ya weigh yourself with every morning... if ya want to know if your losing weight use the same scales every morning....it may not be accurate but it gives you a reference point.... but if ya want to lose weight without effort find a set of scales which weigh 5 lbs under .... :) but dont go back to it again. What I am saying is that no one goes around calibrating dyno's against a known output so who knows how accurate each one is....they are only reference points.

If you really wanna know where ya stand....my suggestion to you is don't be shy.... take it to the strip and have some FUN... cos the proof is in the seat of your pants... as others here have said if it aint pulling low 14's THEN ya know ya got a problem.

regards,

daniel42au
http://members.ozemail.com.au/~daniel42au/

daniel42au · « **Reply #66 on:** August 14, 2006, 08:22:53 PM »

Point taken... but the point I draw between the lights and the strip is that at the street lights I am not behaving like a hoon with high revs.... when the lights change I just put the foot down from idle and let the slush box and the V8 do my torquing.... by the time 60-80kph comes around then I dont wanna play anymore.... because there is no law against nice accelleration. :-)

Quote

Originally posted by 87Z51
which is more useable Torque or Horsepower?

and where?
at the traffic lights... where 95% of us drive?
or the drag strip ... where 5% of us drive?

Same situation either place.The torque is what gets you moving.
A L98 will out run a LT1 to 60mph on torque alone then
two things happen ;
the L98 with it's TPI intake runs out of breath and the LT1 with it's top end manifold comes on line.
Stock for stock a LT1 will run a faster time than a L98 but the L98 will probably run a better 60Ft.

Inherent problem for L98 cars is the torque is so big low down that traction becomes a problem especially in manual cars.
One of the few situations where it is benefical to bleed off some bottom torque so as not to spin up.

BOSCHVETTE · « **Reply #67 on:** August 15, 2006, 07:26:28 AM »

the problem that i have racing off the lights is that with high tyre pressure,cold tyres and the usual build up of oil and crap at the lights i just fry the back tyres into a cloud of smoke, so i tend to wait till the mid of 1st gear before i start to feed the power in.

87Z51 · « **Reply #68 on:** August 16, 2006, 10:53:27 PM »

"I am not behaving like a hoon with high revs.... when the lights change I just put the foot down from idle"

No advantage with a L98 loading up the revs on the line.

At the strip I use the same launch technique I use on the street ;
off idle and nail it = 1.7 60fts
The only difference is how long I keep my foot into it.

nifty · « **Reply #69 on:** August 16, 2006, 11:29:05 PM »

havnt read all posts,but i think gear ratio also has a lot to do with it.years ago i had a (dont laugh) a suzuki sierra 4wd,fitted with the big block 970cc 4 stroke,now this thing had 4:11 gears,and blew most things off at the light.hehe even a compresser mercedes....much to his disgust...hey it happens.but top speed was a killer 110kph.flat out.now if anyone has ever driven one of these thing off road,they will be amazed,low weight,killer low ratio and the abillity to out perform some serious off roaders..think patrols,landcruisers etc..... so how much DOES hp have to do with anything?.... im thinking gear ratios and torque....hp is great for top end stuff, but imagine 500 hp on the street? be real...i would rather be able to pull a wheelstand than run a 200+kph car.

nifty · « **Reply #70 on:** August 16, 2006, 11:54:00 PM »

since my suzuki had the big block 970cc..do i get a membership to the rat pack?;39;39

77CVT · « **Reply #71 on:** August 17, 2006, 01:45:33 PM »

Quote

No advantage with a L98 loading up the revs on the line.

At the strip I use the same launch technique I use on the street ;
off idle and nail it = 1.7 60fts
The only difference is how long I keep my foot into it.

;51 Some good responses here.

1.7 is pretty good traction! ;46

Your ability to use torque is dependant on your tyres. Anything over idle fries mine, which is pretty cool until you can't see where you are going and then it snaps into second and sends you sideways. They hate it when I do that at K Mart!

Your stock intake runners will act as your rev limiter. You can build an L98 for HP but will be a dog over 5000 rpm - with stock runners it is better to have good torque t'out the rev range. (IMHO)

87Z51 · « **Reply #72 on:** August 17, 2006, 10:52:02 PM »

"You can build an L98 for HP but will be a dog over 5000 rpm "
;51

I have siamized stock base ,SLP runners, ported plenum and headers on 100,000 mile engine.
Even with these mods still does not make power over 5000 RPM just makes a lot more than stock below.
The long runner setup, even modified does not lend itself to big revs but makes a sh#t load of bottom end torque.
As stated above it depends if you can get that torque down to the road.

daniel42au · « **Reply #73 on:** August 18, 2006, 04:52:42 PM »

Are we talking about the same thing?

I am talking about traffic lights at the street... and just cruising off without making a scene... ie Revs and SMOKE... :-)

these are two different environments....

My L98 has not gone over 4000rpm except when I agreed to the dyno tuner wishes.... and he found my L98 was puting out the same HP as when it left the factory.... about 160 flywheel hp.

actually I envy you... 400 RWHP is more than enough to please anyone... male or female... AND as they say... what you can't put on the deck is a waste.

So pls share with us what you have done to get 400 RWHP out of an L98?.... and I am hoping that ya dont say ... "i got a crate engine" :-) ... cos I (and the originator of this post) have an L98 to improve without expending too many bucks for the bang....

daniel42au
http://members.ozemail.com.au/~daniel42au/

Quote

Originally posted by BOSCHVETTE
the problem that i have racing off the lights is that with high tyre pressure,cold tyres and the usual build up of oil and crap at the lights i just fry the back tyres into a cloud of smoke, so i tend to wait till the mid of 1st gear before i start to feed the power in.

BOSCHVETTE · « **Reply #74 on:** August 18, 2006, 05:20:37 PM »

Quote

Originally posted by daniel42au
Are we talking about the same thing?

I am talking about traffic lights at the street... and just cruising off without making a scene... ie Revs and SMOKE... :-)

these are two different environments....

actually I envy you... 400 RWHP is more than enough to please anyone... AND as they say... what you cant put on the deck is a waste.

So can pls you share with us what you have done to get 400 RWHP out of an L98?.... and I am hoping that ya dont say ... "i got a crate engine" :-) ... cos I (and the originator of this post) have an L98 which I would like to improve without expending too many bucks for the bang....

daniel42au
http://members.ozemail.com.au/~daniel42au/

Quote
Originally posted by BOSCHVETTE
the problem that i have racing off the lights is that with high tyre pressure,cold tyres and the usual build up of oil and crap at the lights i just fry the back tyres into a cloud of smoke, so i tend to wait till the mid of 1st gear before i start to feed the power in.

daniel
about 18 months ago i blow the old motor up at a corvette drag day so i was in the market for a new motor.i purchased a 4 bolt main block and strocked it to 383 and flowed the alloy heads that were already on it and put a solid roller cam and so on and so on.but the main difference is that i run a miniram intake which is a aftermarket manifold that replaces the long runner TPI injection that you have,and allows me to rev to 6500-7200 if needed.although the motor makes around 500hp if i can improve the computer(eg haltech) and replace the mass air flow meter with a speed density system the engine builder said it should make 560-580hp which would give me about 450 rwhp.easily enough to smoke both supercharged and big block cars.

Vette Obsessed · « **Reply #75 on:** August 18, 2006, 05:26:01 PM »

Quote

Originally posted by daniel42au
Are we talking about the same thing?

Knowing Boschvette, I'd say the answer to that question is YES. ;46 ;41

87Z51 · « **Reply #76 on:** August 18, 2006, 05:37:37 PM »

"he found my L98 was puting out the same HP as when it left the factory.... about 160 flywheel hp"

Should that not be RWHP?
stock L98s come from the factory 240- 245 flywheel Hp.

" share with us what you have done to get 400 RWHP out of an L98?"
Well it was a L98 once until he made it a 383 with miniram

"would like to improve without expending too many bucks for the bang".

From the weight v ET mine is making approx 320 at the flywheel.
Have ZZ4 cam , siamized stock unported base , SLP big tube runners and a home ported plenum with headers.(100K heads never been off)
Running the stock TB v a 58mm made no difference so save your money
Can only go so far with intake mods until you need a cam.

Best bang for buck is headers and a hi flow cat.
Then freebie intake mods ;siamized base works wonders without the big tube runners ,then a cam.

ZZ4 cam is nice can be had for under $250Au ( v $500 for a TPIS cam) and was fitted to ZZ4 crate engine which is a L98 with a carb rated at 355Hp so factory proven combo.
Will lose a little with TPI intake even modded like mine
Need to upgrade valve springs to suit cam ZZ4 / LT4 ones are cheap also.

"My L98 has not gone over 4000rpm"
time to put you foot down ,stock will make power to 4500 before it drops off.

Next?

daniel42au · « **Reply #77 on:** August 19, 2006, 03:01:30 PM »

thanks for that.

yes, your quite right... 160 rwhp is what i meant.

maybe one can never have too much power... and it is only limited by the thickness of one's wallet.

as for me, I am in the process of making some fairly modest improvements... 1.6 gm roller rockers, SLP runners, BBK 52mm throttle body(the original was worn out), hei(?)ignition coil, and a stage 2 transgo shift kit.

I had replaced the original mufflers which were rusted out with a pair of magnaflow mufflers but being in QLD i enjoy driving with the top down too much and the increase in noise got to me so I subsequently replaced them with a pair of stock mufflers from corvette central.

87Z51 · « **Reply #78 on:** August 19, 2006, 09:29:57 PM »

To optimise the 52mm you need to spend 1/2 hour with a die grinder removing the EGR ridges in the plenum behind the TB.

1.6s are a good mod but won't gain you much on the stock whimpy cam.
Will only take you out to .430 / .450 lift where as a stock LT1 cam alone is .447/.459 with 1.5s.
ZZ4 cam gives you .474 / .510 with stock rockers.
Great increase in power with nice street manners.
or match the 1.6s up with the proven Hot cam to get .525 /.525