Trans Am WS6 420

iTrader: (14)

I was discussing turbo applications with a friend the other night, and it seems that to make big boost with some of the bigger turbos out there, you need to be able to spin the motor to a high rpm. I was thinking (dreaming <img src="gr_images/icons/wink.gif" border="0"> ) of an LS1 setup with twin T76 turbos. However these turbos don't really start to build boost until about 4500 rpms. So In order to have a nice power band with those turbos, you would need to be able to turn redline up to around 7500-8000 rpms. What dictates how high a motor can rev?

Sorry if it's a lame question, but I was wondering.....

- Matt

RPM WS6

iTrader: (3)

What dictates how high you can turn the motor safely?

Valvetrain (all of it, in terms of strength and weight), oiling system, bottom end strength, head flow (if you’re planning on making power at real high rpms), fuel system (need injectors that can supply enough fuel fast enough at those rpms), and I’m sure there’s more...

Trans Am WS6 420

iTrader: (14)

ok, so lets say were talking about a custom build stroker, a 427 or something. So assuming the following parts:

Lower End Strength
LQ4 iron block

Valvetrain Strength & Weight
Forged lightweight crank
Forged lightweight Rods
forged lightweight pistons

Head Flow
Set of stage whatever LS6 heads (something bigger that 2.08/1.60 valves)

Fuel System
Twin intank pumps
Large injectors (> 48#/hr)

and of course custom programming

You could turn an LS1 to 8K RPMs? ONly thing I can't venture a guess at would be oiling. Are you thinking a dry sump system?

- Matt

Crazyquik

In a forced induction race engine, you're mainly concerned with the airflow capabilities of the turbos/supercharger unit and not the engine itself. Since hypothetically you want a lot of rpms, a better setup might be a C5R block with a forged crank of near stock stroke. This would allow lower piston speeds than a long stroke engine like a 427. It would displace around 388 with a stock stroke crank.

Dry sump for oiling, oil restrictor pushrods, C5R heads if you use that block, big solid lifter cam, billet rods and pistons. What else? Shaft mounted rockers or a rocker girdle. I'm sure there are a lot of things we haven't even thought of.

J.

Mark IXZD 150

iTrader: (1)

$$$ <img src="gr_grin.gif" border="0"> $$$

ShadowZ28

You could always destrock the engine to a 302 and you should be able get the RPM's up there.

Joe <img src="gr_grin.gif" border="0"> <img src="graemlins/fluffy.gif" border="0" alt="[Fluffy]" /> <img src="graemlins/gr_devil.gif" border="0" alt="[devil]" />

One Monkey

For the record stock LS1 would turn 7500RPM. The question is for how long. (with a upgraded valve train)

Anyways too do this reliably would take a few things.
Things like egnition, fuel pumps, injectors, are a given. But if you are messing with turbos you will know this.
Lets talk about the long block it self.
A 4" stroke as in the 422, 427 will be fine to just under 8000RPM. but the stock stroke would be more reliable.
The stock block would be fine but for this application the C5R block would be the way to go.
LS1, or LS6 heads is all that would really be needed (They can work on the C5R block). You got boost. I would go with a set of LS6. Let your Head porter know the use and He can port it just for that application with the right seats valves and guides for turbos. (And it will rock!!)You will need a set of shaft monted rockers to go with these heads and a nice set of springs.
As for the oiling !! It is a major problem I would go with a Dry sump. (it's really need for that high of a RPM riliably on the LS1) The dry sump will fix 60 % of the oil problem a compatent Engine builder can fix the other 40% with a little work. A good set of rods and piston for the application and Thats it.

You can have a 390ci Turbo charge motor that should make alot of KickAss Power.
Email me if you have any deffinate Questions.
Brent

[ January 09, 2002: Message edited by: One Monkey ]</p>

Pro Stock John

iTrader: (34)

That is a fallacy. You can build a 350ci that will make more power than a 302ci at ANY rpm.

302ci was made to come under a maximum displacement for transam racing. Only reason people buzzed 302s up so high was that they make power up there. But so do 350s.

Tin Indian

I think you have heard some good answers as far as what it would take to safely spin the engine to 7,500 rpm.

Why does your friend think that a engine needs to spin that high to make big boost?

Case in point: A Turbo Buick can make 25+ psi boost with a big turbo spinning the engine no higher than 5,000 rpm. I dont think your friend understands turbo applications to well.

He needs to read a little about turbine hot section A/R ratios and compressor potential. I think he is confusing turbocharging with supercharging or just making guesses.....

Ron,

Tin Indian

And if T76 turbos are not making boost until high rpm, they are too small for the LS1.

I think the real reason is they are limited to less than 6-8 psi boost is because the manufacturer has installed waste gate actuators that limit boost due to the LS1s high static cyl compression.

A properly matched turbo WILL make full boost below 5,000 rpm

If boost tends to increase above 5,000 rpm, its becouse of "boost creep" caused by an improperly matched waste gate actuator.

HP-GURU

What about the intake.

The LS6 intake is going to "shut down" close to 7000 rpm / mid 400rwhp on a 346.

The runner length is JUST TOO LONG. I don't understand why no one else has looked close at these dyno graphs and notice how the power seems soo hard to come by after low to mid 400rwhp - no matter the RPM.

The TQ curve of a resonance tuning issues falls off at an abnormal rate.

racer7088 needs to add to this.

This is the purpose of the spyder intake - high rpm or large power.

In the ford side, they run Vic Jr, Sr converted to EFI on the big turbo/blower cars. This intake feature 8-10" large runners and straight shot down to the intake valve.

LS1powerN20

you would almost definitly want to get the engine balanced and blueprinted.

One Monkey

The intake is a restriction. But there are cars making over 500RWHP with them. In fact all the cars in the 9s have LS6 Intake. There are even cars turning 7500RPM with them and making power. Switching from them too somthing better is deffinatly going to make more power. But there are not as restricted as most people like too belive.

Now after that said, on a Turbo application turning over 7500RPM Tring one of these Sheet metal Intake just might work for more power.
But thats somthing that would be tested too get right.

HP-GURU

But what happens if intake is resonanse tuned for wrong range is it will actually "shut down" on you, and make increasing HP harder and harder to come by.

We've seen this alot of times in the ford sides like I said, the super long runner intakes make nice tq and HP in low rpm situation,

the medium runner LS6 allows a motor to make 500rwhp, but after about 430-450rwhp the power gets harder and harder to come by.

Like I said, pay close attention to the dyno graphs. From the picture I could see there is a "restriction", one would guess the Stage III heads should be good to 600rwhp naturally.

Dennis

p99ta

[quote]Originally posted by LS1powerN20:
<strong>you would almost definitly want to get the engine balanced and blueprinted.</strong><hr></blockquote>

Everything that everyone says is important... but this guy is right on the money... one of the things that happens is that a rod will want to split apart because of centripetal forces. Try swinging your arm in a circle. Your hand feels like it wants to pop off right? Think what it can be like for an unbalanced/unblueprinted motor... I would recommend forged rods too... and forged crank if possible... been doing lots of reading... cause whenever i get a chance i am supercharing a 455 for my 75 firebird <img src="gr_stretch.gif" border="0">

Chris

Rich in NC

I am always confused about the RPM numbers listed. Unless it says "On a 346ci stage II head motor it spins at 4500", the number is worthless.

I'd be willing to bet a 346ci motor pushes more air out its exhaust at 3000rpm than a 1.8L Honduh motor at 5000.. It's simple displacement, the engine is nothing but an air pump.

Pro Stock John

iTrader: (34)

-Solid roller
-Dry sump
-Custom intake that flows up there (LS6 won't)
-Forged internals, stock stroke
-Big valve heads
-Studded heads

[ January 09, 2002: Message edited by: Pro Stock John ]</p>

racer7088

Actually the stock LS6 manifold seems very happy even up to 7500 but that's probably it and a bigger shorter mainfold would make more up there probably especially on the bigger engines. We actually had the stock LS6 on when we went 9.90s at 136 with the 418 so it is a lot better than people think. I think Judson was shifting it around the lower or mid 7000 rpm range. The bigger stroker has lower peak power than the earlier smaller motors did maybe around 6800 or so I think. <img src="graemlins/burnout.gif" border="0" alt="[Burnout]" />

Marty

[quote]Originally posted by HP-GURU:
<strong>What about the intake.

The LS6 intake is going to "shut down" close to 7000 rpm / mid 400rwhp on a 346.

The runner length is JUST TOO LONG. I don't understand why no one else has looked close at these dyno graphs and notice how the power seems soo hard to come by after low to mid 400rwhp - no matter the RPM.

The TQ curve of a resonance tuning issues falls off at an abnormal rate.

racer7088 needs to add to this.

This is the purpose of the spyder intake - high rpm or large power.

In the ford side, they run Vic Jr, Sr converted to EFI on the big turbo/blower cars. This intake feature 8-10" large runners and straight shot down to the intake valve.</strong><hr></blockquote>

So can the new holley be made to pull higher RPM or are you gonna have to go with a custom(like hogans or the spyder)?

[ January 10, 2002: Message edited by: Marty ]</p>

DCPunkSteve

I don't know why you all think you need something as exoctic as dry sump oiling just to turn it up over 7500rpm. I'm glad none of you are budgeting any of my finances. Just a little backround, people have built LT1s that turn nearly 8000rpm on just a stock pump. The LS1 doesn't really have an oiling problem. In fact I'd be willing to be that the stock bottem end, (minus pistions) would be able to hold up, if they were properly balenced, and maybe even cryo-treated. It's you valve trane thats going to suffer. I would go with a solid roller cam, springs, and possibly shaft mount rockers.
Also there are alot of guys running the T76 turbotech kit, and none of them seem to have any complaints about spool up time.