Changing turbo setup

[DAVe3283]

I've had my motor built for about 5 years now, and I have an old Trent Nell / EPR turbo kit. It's a S371 with a clipped 74mm turbine. It has made 700+ HP but I mostly run it on a 660 HP tune to try and extend the life of the turbo, with limited success.

I've been toying with the idea of compounds since I built this motor, and am thinking it's about time to pull the trigger.

There's a local shop (Big Twin Diesel) that is recommending a Garrett GTX 4094 (68mm) over a 4718 (88mm). I don't know much about the Garrett stuff, and am curious if anyone has run a setup like this, how did you like it?

Motor setup: SAC75 injectors, 12mm CP3, Carrillo rods, Mahle race cast pistons, Comp Cams CCA-132-502-12.

Currently it won't build any boost below 2000 RPM, but my converter and shift strategy is setup so that works fine, even towing. I'd imagine compounds would do a bit better down low, but what I'm really hoping is to clean up smoke at WOT and get some better reliability out of the turbo(s).

So what do y'all think, will I be happy moving to Garrett ball bearing compound turbos?

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[MAXX IT OUT]

I have similar sized compound turbos but Borg Warner, to what they suggesting on my truck with a stock parts engine and it drives better than the single 69mm did. I generally drive on a 530hp tune, with Marks tuning, it's a smooth power transition, plus to there is no new bay windows which I see as a benefit.

 

[Chevy1925]

i know the gt4094 was never a big hit. it was laggy for the size and didnt make the power people expected. the GTX 4094, i have no experience with. the GTX are suppose to have a new center section design and better turbine sides than the GT versions so it might be a completely different turbo now. i know @MarkBroviak would know.

 

[MarkBroviak]

The GTX is a better unit than the previous generations but I would rather have the Borg SXE369 than the garrett unit but that's my preference.

 

[Bdsankey]

How do you want to use the truck? What kind of HP goal? I've played with a few of the Garret line and like Mark I think the borgs are a much better value at very very similar performance. The GT4094 was a lazy sow, no experience with the GTX line in that size.


A 369/488 setup is pretty hard to beat for the "hot street" type truck that does occasional towing. If it was something to tow 24/7 I personally really like a 364.5/68 and 480. I've used this combo on a few trucks and been very pleased.

 

[Chevy1925]

A 369/488 setup is pretty hard to beat for the "hot street" type truck that does occasional towing.

this is where i was headed with the Limo. it was either going to be the sxe366 or 369.

 

[Bdsankey]

this is where i was headed with the Limo. it was either going to be the sxe366 or 369.

They flat out work well and are extremely budget friendly which is not a common occurrence these days haha.

 

[DAVe3283]

The truck does tow fairly often, but you have to remember my baseline for acceptable lag is this worn-out S371. With the converter and trans tuning I can make it work. It is only annoying in 1st gear; once I am rolling it is pretty responsive.

I certainly appreciate the value of the Borg turbos, but they have not held up for me. This is my 3rd failure in 5 years, so I won't be going with a 300 frame on this motor again. Maybe they would last better in a compound setup, but this experience has pretty well soured me on them.

As for power, I don't have any current plans to bump up injector size, so I will probably push these SAC75s to around 2000 μs and see where that lands me power wise. I would imagine the 800 HP range, given 1800 μs on this S371 has me right at 700 HP. The bigger goal is to clean up smoke and have the dang turbo setup hold together for more than 1-2 years.

 

[Bdsankey]

The truck does tow fairly often, but you have to remember my baseline for acceptable lag is this worn-out S371. With the converter and trans tuning I can make it work. It is only annoying in 1st gear; once I am rolling it is pretty responsive.

I certainly appreciate the value of the Borg turbos, but they have not held up for me. This is my 3rd failure in 5 years, so I won't be going with a 300 frame on this motor again. Maybe they would last better in a compound setup, but this experience has pretty well soured me on them.

As for power, I don't have any current plans to bump up injector size, so I will probably push these SAC75s to around 2000 μs and see where that lands me power wise. I would imagine the 800 HP range, given 1800 μs on this S371 has me right at 700 HP. The bigger goal is to clean up smoke and have the dang turbo setup hold together for more than 1-2 years.

Are you watching drive pressure? It's very possible you're killing them by simply driving them too hard. In that case any similar sized turbo will die the same death.

S4/S4 works decently well. Some guys don't like them. I've only got first hand experience with one S4/S4 setup and it's been pretty decent (467/87 and 488/96).

 

[DAVe3283]

Are you watching drive pressure? It's very possible you're killing them by simply driving them too hard. In that case any similar sized turbo will die the same death.

S4/S4 works decently well. Some guys don't like them. I've only got first hand experience with one S4/S4 setup and it's been pretty decent (467/87 and 488/96).

No, I don't have a drive pressure gauge or a wastegate. It wouldn't surprise me if I was just asking too much out of it and that is why it won't last.

The S467 + S488 setup you mentioned is something I have considered as well. Would the S467 be more responsive than the GTX 4094? Or in the same ballpark?

I guess the real question here is if compounds will help prevent the high-pressure charger from giving up the ghost at 700+ HP like a single 71mm does.

 

[Bdsankey]

No, I don't have a drive pressure gauge or a wastegate. It wouldn't surprise me if I was just asking too much out of it and that is why it won't last.

The S467 + S488 setup you mentioned is something I have considered as well. Would the S467 be more responsive than the GTX 4094? Or in the same ballpark?

I guess the real question here is if compounds will help prevent the high-pressure charger from giving up the ghost at 700+ HP like a single 71mm does.

You're taxing each charger far less.

Put it this way, one of my customers had 40k on his 364.5/480 setup. He drives like a mad man (built motor, 100%, billet trans etc) and he killed the borg SXE atmo that had been rebuilt twice by another shop before it came here. He wanted to upgrade and plans on making more steam down the line so he went 488/96.

If he hasn't yet killed that valley charger (at ~65k miles now) then I doubt you will.

 

[Chevy1925]

I guess the real question here is if compounds will help prevent the high-pressure charger from giving up the ghost at 700+ HP like a single 71mm does.

yes, 100%. thats why my stock valley charger lasted as long as it did. it keeps the valley charger in its map while the big charger increases pressure in front of it.

thats why the BW turbo will last far longer. you could even leave the 371 there and compound it and it would last far longer.

also, just adding more cfm from compounds with the current tune you run may be a decent bump in power just due to burning up the rest of the fuel you are leaving behind currently.

 

[rcr1978]

Brad

Are all the guys running the small turbine 64.5 with a standard turbine housing? I was considering going that route but trying a gated housing along with it.

 

[Bdsankey]

Brad

Are all the guys running the small turbine 64.5 with a standard turbine housing? I was considering going that route but trying a gated housing along with it.

3x big turbine and 1x small turbine.

 

[DAVe3283]

Took almost 7 months, but the compounds are done. Well, almost done. The shop managed to crack the left front accessory bracket that holds my air compressor, so I have to get the replacement powder coated. And the tuning has a ways to go. A million little things because I am OCD and very particular about my truck, but on the whole, it is back on the road!



Firebird had a midnight drag event last night, and despite almost getting rained out, managed to get one run in. Launched a bit soft in 4x4 (first time on the new setup) and put down a 12.714 @ 106.



I had screwed up the tune and only updated 3 of the 4 pulsewidth tables, and naturally forgot the most important one (main pulse when pilot is off), so 4 seconds into the run it dropped from 2000μs to 1600μs, and I ran 2/3 of the track on the old single-turbo fueling. I think it should have an easy 12.5 in it next time with the fixed tune, especially if I can improve the launch.

Here is the race as seen from my friend's Volvo C40 Recharge Pure Electric:

 

[Chevy1925]

I like the secondary a/c lines you got goin on there

But hell yeah dave! That’s awesome. We need some turbo noise though!

 

[TheBac]

IIRC, cant you buy separate AC fittings and hose and make custom lines to route around twin setups? Obviously a shop has to crimp the lines, but I thought it could be done?

Looks good Dave. Shoot for 11.80s.

 

[PureHybrid]

How heavy is this thing?

 

[JoshH]

Looks like you ended up with the Garrett turbos? What sizes did you end up with?

 

[DAVe3283]

I like the secondary a/c lines you got goin on there

But hell yeah dave! That’s awesome. We need some turbo noise though!

Heh, that was the shop recharging the A/C. Pity they didn't vacuum any of the air out first, or put on a new dryer, since it was open to the moist air for 6 months... Oh well, I recovered it and vacuumed the water out (took 4 hours to boil off), and A/C actually works now.

IIRC, cant you buy separate AC fittings and hose and make custom lines to route around twin setups? Obviously a shop has to crimp the lines, but I thought it could be done?

Looks good Dave. Shoot for 11.80s.

I plan to redo the lines, since the shop just mangled up the factory lines to fit. I have the crimpers to make custom lines (had to get rear A/C in my Duraburb somehow...), but I might wait until I do the LBZ cooling stack swap this fall to redo the lines. I will be putting the ambulance package condenser on at that point which takes a different liquid and discharge line. Do it all at once, save some effort, especially since this setup works as-is now.

I would love to see an 11.99 or faster, but I think I am about out of injector, and this rig is heavy.

How heavy is this thing?

She's chunky. It has a 55 gallon fuel tank, lift gate, gooseneck hitch, aftermarket front and rear receivers, etc.
I weighed it yesterday at ~8,100 lbs with just under half a tank. I expect race weight will be between 8,000 (⅛ tank) and 8,300 (full tank).

Looks like you ended up with the Garrett turbos? What sizes did you end up with?

Ended up with:

• GTX4088R (65/88.4mm w/54 trim compressor, 77/68mm w/78 trim turbine)
• GT4718R (88/118mm w/56 trim compressor, 92.7mm w/82 trim turbine)

They spool a bit better than the S371 single, but my cam has always been a limiting factor trying to get on top of things below 2000 RPM. But my torque converter and shift strategy is set up to deal with that, so it actually drives pretty well except for 1st gear from a dead stop.