gt4088r.....A/R?

[95SleeperAcheiva]

I've had really bad luck lately on my cars.

Threw a rod on my S-10, week later threw a rod on my quad 4 achieva.

Last x-mas, popped a head gasket on the cutlass.

So I'm rebuilding the cutlass because I don't have the time to finish the drag achieva.
And i miss my car and want a street toy.

So... pulling the motor, LQ1, out later next week for a full rebuild, complete with new and stronger lower end, some p&p work, injectors etc....
I have/had a dodge truck turbo to drop in there but upon tearing it down....it's junk.

So, following Mars advice, and trying to learn more about boost, I looked into the GT4088r.
I've learned how to read the boost maps, I understand the maps....i think.

Now how to apply that data to understanding if my motor can handle that. How much can she breath to avoid the "surge" I've read about? And on the turbine side, what is .89 A/R vs the other 1,2,3,4 models that they show with different A/R's? How is that going to effect or what is that going to effect?

Still an automatic, high stall converter being made, and beefing up the trans, with help from a tranny guru.

My goal is, to not have another M5 pull on me like I'm in reverse, and still drive this thing daily, no emissions required. thx

[robertisaar]

surge on a LQ1 would be hard, with a properly sized compressor... if you look at turbo maps, you'll see the surge line to the left of the map, and with the map going airmass from left to right, you can deduce that surge happens at lower airflow for a given pressure. seeing as how the LQ1 breathes deep, should be hard to get into. that's the simple explanation anyways.

also simple ex: turbine A/R basically determines what RPM (at WOT) you'll start making boost at. lower A/R = lower boost threshold. however, too low of an A/R will essentially choke the top end and you'll end up with a LOT of pressure between the head and the turbine, which kills power, increases EGTs, lots of bad stuff. on the other side of the coin, a REALLY big A/R will significantly the raise boost threshold, so the engine will essentially act N/A until that point, but when it does make boost...... monster torque multiplier.



ideally.... you'll make a comprimise somewhere between the two extremes for turbine A/R. while a really high A/R would make awesome peak HP/TQ numbers, it wouldn't be anywhere near as much fun to drive on the street and would probably be slower on the strip than a car with a more reasonable A/R.

the garrett turbo website has a decent introduction to turbos. http://www.turbobygarrett.com/turbobygarrett/

if you really want to spend money.... the variable A/R units are just magical in operation.

[Mars]

I've got a .95 turbine on mine, and I'd go smaller on a 3500 if I was to do it over. (well now that I'm planning a 3.9, it'll likely be OK)

Don't go any bigger than a .95 I say on your DOHC. It'll still sream on the top end and it'll spool at a decent RPM.

[95SleeperAcheiva]

rgr that thx

[timg]

On the GT4088R, turbine A/R was pretty large compared with what people are used to for a T4 turbo. All of them should work, but the smaller ones trade top end for spool and the larger ones trade response and low end for power.

Consider this turbo. Borg Warner S300SX FMW.

http://www.full-race.com/store/turbos/borgwarner-airwerks/borgwarner-s300sx-fmw-turbo.html

It's much newer and cheaper than the GT4088R. The GT4088R is an awesome turbo, but this should get you the same or better performance for less $$. It's also only oil cooled, so you wouldn't have to worry about running water lines to the turbo.

Tim

[Mars]

^ jesus I like the sounds of that turbo as well...