turbo6man

iTrader: (5)

HI I am trying to build my new motor based on a 1/4 mile goal of 170 mph at 3690 lbs. I have been 161.5mph on the old 370/s484 combo in my sig. I know I want to do this with a garret Gt5533-94 turbo. I am going to use an LSX block but I have read a ton and talked to alot of people and get alot of different answers. I have been told that the cu inch range for that turbo should be between 370 and 416 cu inches. From what I read I think I want to be in the 4.125 bore by 3.8" stroke range. I have called piston manufactures but get different answers So my question is : does anybody know which bore/stroke combo provides the most cu inches in the 380 to 416 range and provides good ring to top of piston distance as well as piston pin to oil ring clearance and also does not come out of the bottom of the LSX bore(std deck height) to much. Trying to make as much torque to spool the turbo for street use without getting back pressure as well as durability of parts for 1300 rwhp.

Kmspeedie

iTrader: (1)

autozone got some nice stuff in the back by the oil..


lol look at thompson, they give you HP rated motors

Exidous

iTrader: (11)

4.125" bore for sure. Around a 3.8" stroke is fine maybe even a 3.9". At a 3.8" or 3.9" stroke piston acceleration shouldn't be an issue unless you want crazy RPM's so a long rod isn't necessary. You may end up with a 6.125" rod and adjust the pin height as necessary. Around a 1.165" for a 3.9" stroke. 1.215" for a 3.8" stroke.

turbo6man

iTrader: (5)

This is the type of information I am looking for, I do not know how to figure out in that range of stroke which will provide the use of a piston that will be the most reliable for that kind of power. I do not want to use a shorter rod then have the piston be better for ring distances but be to heavy or use a longer rod that puts the piston pin and rings in a location which weakens the pistons.
Why do I see so many kits for the 4.00" stroke. Also Callies makes the dragonslayer in a stock stroke or 4.00" only, If I want a stroke between those two you have to step up to the magnum and special order. It also makes the pistons special order. I am questioning myself because I would think if it was a good idea they would have rotating assembly's for sale in this stroke area.

rotary1307cc

iTrader: (5)

Yeah stock of 3.622 and smaller bore

Why would you knock out a new LSX to 4.125?? Seems like a waste.

Orr89rocz

iTrader: (13)

4.125 bore 3.622 stock stroke 387"
6.125 rod
Leaves 1.304 height je piston. Turn it 7000-7500 and call it a day. Good thick piston

But the typical 4.030 bore 4" stroke combos have gone 7's too and 7-7.3k rpm as well so could go that direction as well since likely more parts designed for 4" stroke.

turbo6man

iTrader: (5)

Well im still in the deciding stage, but have gotten suggestions and prices from a few of the people who are always helping on this sight. And both suggested 4.125" bore but the stroke differed from stock stroke to 3.875" stroke. Keep in mind im trying to maximize the street and spool up maners to the gt5533-94 without getting to much backpressure by over cubic inching the motor. I realy want to think this through and get as many ideas as I can because i want to be involved and feel like i chose my rotating assembly wisely.
Thank you to all for any input given. ......

turbo6man

iTrader: (5)

Awesome info. I need to get hard piston data on the specs of the 3.8" and 3.9" stroke then compare it to the above stroke as well as cost difference of the pistons. Since they are not a shelf piston, should i e-mail the manufacture to get thos specs?

gnx7

iTrader: (28)

I know that many guys run a 3.9" stroke crank as the journals are thicker/stronger. This really only matters above 1500hp. The 4" crank when pushed to the limit can crack in the journal area. Crèam Dream in Canada aka tirefryin_s10 did crack his.... and then opted for the 3.9" stroke on his latest refreshening. His car does run 7's though and he spins it well above 8000rpm.

http://www.yellowbullet.com/forum/sh...432473&page=51

DavidBoren

3.9" stroke, with 6.25" rods, and 1.04" pistons gives you a rod ratio of 1.60, and a 3.8" crank with 6.3" rods with 1.04" pistons gives you a rod ratio of 1.66, which is about the same ratio as the factory 3.62" crank and factory 6.098" rods.

3.8" stroke and 4.125" bore gives you 406ci, which is right where you are looking for.

Orr89rocz

iTrader: (13)

I know je lists all their available shelf piston combinations.

Basically subtract half the stroke and the rod length from the deck height of the block to get piston height required. Then have to find a piston with those specs. What i'd be asking is how far down is the top ring from the piston crown? Farther down is better since its away from heat. If its closer to top make sure you add in more ring gap. A taller piston height should have alittle more distance from crown to first ring but it depends on how the manufacturer set up the piston.

DavidBoren

Having a good amount of meat above the top ring is important, especially at these power levels. And a 1.04" piston still gives you plenty of room for a good ring pack.

I think the shorter, and consequently lighter, piston is a better choice for the longer rod it allows. And I think the higher rod ratio is worth using custom pistons if that's what it takes.

RonA

iTrader: (1)

I can't imagine a 1.04 ch piston as having plenty of room for a ring pack and good top ring to top of piston.

DavidBoren

If you don't feel comfortable with a 1.04" piston height, then you can use a 1.115" tall piston which is the same height as every 4" stroke/6.125" rod combination out there, and use a 6.25" rod and 3.75" crank. Puts you at a rod ratio of 1.666 and 400ci of displacement on a 4.125" bore. Couple that with some NFI mms235's that have been mamo-fied, and you're probably looking at over 500rwhp without any boost, so breaking 1000+ with your turbo should be a cake walk.

Orr89rocz

iTrader: (13)

I like that combination, 4" stroke has made the power the OP is looking for. 3.75" stroke 4.125 bore is basically a sbc 400. They work too. Dont need to turn it over 7k either if the heads/cam/intake are doing their job
.

rotary1307cc

iTrader: (5)

Learn how to read a compressor map and you will see that turbo will run in better effiency with a smaller motor at a higher pressure ratio

DavidBoren

AND... If you need a smaller displacement to better use that turbo, then run your 4.125" bore with a stock stroke length of 3.622" with a 1.129" tall piston. This gives you a rod ratio of 1.74 and 387 cubes.

Still would use the CNC+ (aka mamo-fied) mms235's with Tony's NFI package.

Orr89rocz

iTrader: (13)

True but for a mixed use street strip car, the larger cubes should be more responsive when rolling around. 380-400 cubes is a good area to be in with that map, figuring 150-155 lbs min for 1300 whp. Only gonna need closer to 1200 for 170 mph traps however. Looking at 2.6-2.8 pressure ratio on a decent built 380-400 inch motor

rotary1307cc

iTrader: (5)

That is perty much running you off the map at that PR . I don't get why people are scared of boost.

The smaller cube motor you are stronger everywhere plus the turbo is happier. I don't get the need cube thing. I run a 376 with a gt5t on a tight converter and there is nothing to spool. And I am almost strictly street

Much stronger crank. Stronger piston, more skirt contact, more HG area, thicker cylinder wall, happy turbo. I don't get it

Orr89rocz

iTrader: (13)

150 lb min is on edge of the map regardless of pr

Certainly dont need cubes but its not going to hurt. Like said 370-400 is not a bad displacement to be for that turbo

If you were going to shoot for ideal efficiency, you have to go alot bigger than that 94mm wheel to land in the peak island. What does that give you tho? Overly sized turbo for the job at hand and only saving a few degs of iat. Cooler will overcome that if sized well, esp air water

Example. That turbo peaks at 76% efficiency. If you chose a turbo that gave you 20 psi at 76% efficiency thats 312 deg f air outlets. A turbo at 63% would give 364 deg f outlets. Good bit different but thats on the extreme variance of islands on that turbo. On the outer edge you may see only a 4-5% eff difference between 3.0 pr and a 2.6 pr, 370 cube vs 400 cube lets say. Every little bit of hp helps but depends what you are after.

I just know a good 408" setup with a 91-94 wheel will run high 7's at a pr in the 2.6-2.7 range in a 3500 lb setup. Air water manages iat and thats 1240 ish whp.

I recommended a 3.6 stroke 4.125 bore setup for better piston size and large bore for big valve size, more flow for making more power on less boost where possible. Different ways to do things