How Much Hp?

[himata13]

i am still searching around on how to add more HP tp my SS and i am really falling in love with a turbo set but how much HP can this motors hold?? i know i will have to beef up the tranny but what would the motor hold along?

[Parriott31]

you will need bigger injectors right off the stock lq9 a capable of around 450 hp but it will start needin some upgrades after that too many to list.... also be careful puttin on the turbos they are really hard on a motor with over 100,000 miles at least thats what i have been told...

[himata13]

motor feels healthy. what i am going to do is change the timing chain.

but how much HP can the block holds? i know i will have to get injectors, a pump but how much will the block hold?

[misterp]

motor feels healthy. what i am going to do is change the timing chain.

but how much HP can the block holds? i know i will have to get injectors, a pump but how much will the block hold?

The iron truck blocks are stout - far more than 750+ crankshaft hp, provided you keep the stock crank/rods/pistons in the motor and install premium valvetrain; if you replace the cast pistons with forged pistons then 1000+ is not out of the question, if built and tuned right. To get meaningful power you need RPM, and that will require replacing a lot of the valvetrain because the stock stuff is not all that reliable above 5800-rpm. Many folks will also suggest you replace the factory rod bolts with a set of aftermarket ones (not a bad idea) but I know that a bone stock LQ4 shortblock with Dart heads run to failure on the dyno reached 8900-rpm before the factory rod bolts let go, so the bottom-end is a lot stronger than people give credit. The factory PCM will not even rev past 8000 and the trans won't take beyond 7200-rpm without extreme modification so the rod bolts are not as big a problem as most folks believe IMO. All this assumes the motor is tuned correctly, when dealing with this much torque at those engine RPMs any detonation will shatter a factory piston and it's game over.

 

Going turbo is a *great* idea - my suggestion is that you buy an electronic boost controller so that you can program/vary the boost and tailor it to the truck/motor, that way you can launch with a limited/controlled amount of boost and as the RPMs pass peak torque (4100-ish) then ramp-up the boost to keep the cylinder pressure up... Factory pistons will take RPM, but not more than 525-550 ft-lbs torque (that's an internet rule!) so build the motor to make 525-550 ft-lbs at 6500+ RPM and that will be 700+ hp

 

Mr. P.

[KDavis04ss]

Mr. P what size turbo do you think will make these trucks scream? with all supporting mods of course. since the OP was interested in a turbo setup he might be interested in knowing this also along with me.

[misterp]

Mr. P what size turbo do you think will make these trucks scream? with all supporting mods of course. since the OP was interested in a turbo setup he might be interested in knowing this also along with me.

Can't answer that, I'm a centrifugal guy! I've not taken the time to study compressor maps & AR factors etc. There's a lot to sizing a turbo, and turbo-specific camming matters too.

 

Mr. P.

[himata13]

thanks for the info Mr P!

[chpspecial]

 

Going turbo is a *great* idea - my suggestion is that you buy an electronic boost controller so that you can program/vary the boost and tailor it to the truck/motor, that way you can launch with a limited/controlled amount of boost and as the RPMs pass peak torque (4100-ish) then ramp-up the boost to keep the cylinder pressure up... Factory pistons will take RPM, but not more than 525-550 ft-lbs torque (that's an internet rule!) so build the motor to make 525-550 ft-lbs at 6500+ RPM and that will be 700+ hp

 

Mr. P.

 

 

Hey Mr. P,

I have been reading your past post as well as this one and it got me thinking... I came up with a plan to do as you said. All it would take is some wiring, a solenoid and a window switch to do what you said. As I was about to put everything together I thought about it more and realized that most people gave a big enough TC that puts the shifts recovery above peak torque RPM... So after realizing that, is there really a gain in having (what I am going to call) variable boost. Another thing, once the wastegate on a turbo has closed and added more PSI, the turbo will not bleed off boost, unless you lift off the throttle. I.E. if you initial boost is say 12# and your variable boost comes in to add 5# for a total of 17# then you will get 17# until you lift off the throttle, No matter what RPM the engine is at. So, I assumed that this will only be beneficial to first gear/2wd truck... Know, a centri supercharger is a differnt matter, and I can see this working with them...

[misterp]

Hey Mr. P,

I have been reading your past post as well as this one and it got me thinking... I came up with a plan to do as you said. All it would take is some wiring, a solenoid and a window switch to do what you said. As I was about to put everything together I thought about it more and realized that most people gave a big enough TC that puts the shifts recovery above peak torque RPM... So after realizing that, is there really a gain in having (what I am going to call) variable boost. Another thing, once the wastegate on a turbo has closed and added more PSI, the turbo will not bleed off boost, unless you lift off the throttle. I.E. if you initial boost is say 12# and your variable boost comes in to add 5# for a total of 17# then you will get 17# until you lift off the throttle, No matter what RPM the engine is at. So, I assumed that this will only be beneficial to first gear/2wd truck... Know, a centri supercharger is a differnt matter, and I can see this working with them...

To completely disclose, I first read about programmable boost control a few years ago when I saw this bad-ass video:

 

He dropped about 3/4-second from his time by using a fully programmable electronic wastegate system, these are not cheap; you can program a "boost profile" for each different gear & RPM or MPH, that way you can put down as much torque as the tires can handle at any point in the run.

 

But there is another strategy - and that is, you can use a regular wastegate and have max boost all the time, but then retard timing in the spark table to take some power out of the motor and keep the wheels from blowing loose...

 

But I am not talking about traction/tire life; my point was towards engine cylinder pressure and making big power on factory pistons. The simple point is, the factory pistons are only strong enough to handle the cylinder pressure that generates 525-550 ft-lbs of torque, that is the physical limit of the upper ring land (assuming NO detonation or other mal-combustion) and after 550 ft-lbs the piston ring wants to rip out of the upper ring land on the stock piston. So the alternative strategy is to make 500-525 ft-lbs at much higher RPM, and let RPM win your races for you. The factory pistons will handle 7000-RPM no problem, as long as you do not exceed the cylinder pressure for which they were designed.

 

On a naturally aspirated motor, it breathes in a certain volume of air and compresses that mixture - the actual real-world PSI of that compressed gas will be about 200-250 PSI (again, on a naturally aspirated motor). The problem is, for lots of reasons when you pass 4000-RPM the naturally aspirated motor cannot breathe as much air, and we see this as torque peaking at 4000-RPM, and torque falling as RPM climbs past 4000-RPM torque peak - the reason why torque falls is because cylinder pressure is falling, because the cylinders contain less air, because VE is falling... OTOH, if you use forced-induction, the cylinder pressure never falls off, because the cylinder is always filled with air (if your blower is working right!).

 

When using forced induction on a stock piston you have to accept the physical strength of the piston and make sure that you are not building too much cylinder pressure that would either (1) rip the top ring out of the ring land, or (2) push the head gasket out; since the motor naturally wants to build high cylinder pressure at peak torque RPM, you have to be midful of the amount of boost (cylinder pressure) at the peak torque RPM - after that point, because cylinder pressure is falling you are free to add MORE boost to shore-up and maintain the same cylinder pressure that was present at peak torque! This is why I believe in large centrifugal blowers, you pulley them to hit a modest 7-9 psi at peak torque (4000-4500 RPM) and after that point when cylinder pressure naturally begins falling you can increase the boost level to 10-12 pounds - this is why big centrifugals get away with running 12-psi boost on a stock motor, is because at 4500-RPM they are still only making 8-psi and not exceeding a safe cylinder pressure level.

 

Using an aftermarket piston will change things, because those pistons are made with a thicker (stronger) top land, and made from stronger alloy so they can take higher cylinder pressures without damage; add in a premium head gasket that will hold well and now you can have cylinder pressures in the 500-600psi range rather than the stock 200-250psi range, and hence making 1000-ft-lbs of torque rather than 400-ish ft-lbs...

 

Power wins races.

[Horse]power is derived from torque.

Torque is derived from cylinder pressure.

Everything about engines is the study of pressures.

 

Anyways - to achieve that kind of control with a turbo I would find the best programmable boost controller you could afford, or yes you could implement a 2-stage "hi" and "low" boost wastegate setup and run low-boost (8-psi?) to 5500-RPM and then up the pressure in the top-end of the RPM range (when it's safer to bring that extra boost in).

 

Mr. P.

Edited January 28, 2011 by Mr. P. (see edit history)