GTM twin turbo winter project.

[Kalstar]

Staying with my budget build style. I am looking to stay below $4000 for the build (plus another $1000 for the rebuilt of the spare engine and purchase of the trans side plate). I chose the Holsets turbos because they are OEM units, built for longevity and are extremely reasonable in price. I like that they have internal wastegates for ease and cleanliness of install. The newly produced Turbosmart internal waste-gates allow for adjustably from a low 3psi all the way up to 22psi The engine and both turbos will be fully rebuilt and all other parts will be brand new. I will also have a fully rebuilt spare engine and the ring/pin side plate to help support the current trans. Goal is not to go too high on the power output to start with (the car is already crazy fast without turbos) but have the ability to turn up the wick when "needed".


So here is my list, am I overlooking anything?


(1) Oil sender adapter/oil line feed
(1) -4 feed .040 restrictors
(2)-10 return w/ hose Y
(2) oil flange kits
(1)-4 T kit for twin turbo set up
(2) Turbosmart internal wastgate(s)
(1) 50mm BOV center mounted 6" from TB
(2) turbos twin (Holset hy35) 58mm/65ar
(2) turbo blankets
(1) water to air twin inlet intercooler
Fab work by local shop
$2608

Engine
Ls5.3 L33 (stock bore) recommended for higher boost and clamp force.
243 heads (came on boneyard engine) mild home ported
Stock LS6 corvette exhaust manifolds with copper gaskets (on current engine)
Fel-pro head gaskets
Katech head studs
918 Valve springs (in current engine)
King cam bearings
OEM rings
OEM rod/main bearings
Katech studs rod/main
LS3 lifters
Comp Cam xr269 (in current engine)
LS3 90mm TB
Typhoon 90 intake*
ls9 injectors 58lbs (have them from a past build)
Areomotive fuel rails (have them from a past build)
$1193


Spare engine (currently in car)
LS6 springs (replacement for parts used in turbo engine)
LS9 cam (replacement for parts used in turbo engine)
New cam/main/rod bearings replaced with GM parts
New lifters, head gaskets and stock GM bolts.
$510

Trans
side plate
possibly 930 conversion
$425 (side plate only)

If I go with the 930 conversion there is quite a bit of pros and cons. The pros is a much stronger trans with a 60mph first gear. Cons are too tall for extended highway use and it is only a 4 speed. The trans is $4000, adapter $1400, starter $180 and clutch $875. The set up will be about $6455.00 all in. I could sell my G50 (with only 24k miles) with everything (starter/clutch/adapter) for $5500 so in the long run the conversion would be less then $1000. I have confirmed the g50 and 930 are both compatible with the F5R rod shift (which I like the feel of).


Both short blocks will be rebuilt at the same time. The engine builder is allowing me to work beside him to learn. I figured 2 blocks...he works on one, I work on the other...why not. Besides the stock parts for the spare 5.3 was under $360 (not including the cam and springs). He said he would charge me $400 to build just one or the same $400 for both if I help. According to BW Matchbot (turbo sizing program) the output for this engine and turbos is 915.3hp 808.7tq at 18psi with a 6800 redline (though peak power is made nearly 1000 rpm lower). This build*http://www.lsxtv.com/news/video-twin-turbo-5-3l-nova-wagon-on-the-dyno/ confirms those numbers (800 whp through a 4l80E is roughly 950 crank).*

So before I start ordering the parts, what are the opinions on this plan?*I am fairly new to this (only owned a few factory turbo'ed cars) so I am wide open to suggestions and discussion......

[crash]

As I said before, I have not done a lot of hands on work with turbos or super chargers either, so I am watching this with anticipation. Please keep us posted as to how things are going and what is happening.

[wallace18]

I would add a oil cooler if you do not already have one. Turbos add lots of heat to the oil. JMO

[Kalstar]

Thx Crash, glad I purchased the over kill parts from you. Thanx for the suggestion way back then... they will come in handy now.

Tom good call on the oil cooler, I will add that to my list.

[ExtraTitanian]

First and foremost, I'd second, third and fourth what wallace said about the oil cooler, your turbos are, by far, the hottest things in your engine bay. In addition, I don't think your list included a boost controller of any sort, preferably one that'll cut your boost down to 5 psi or so the moment it detects detonation so you don't end up sending a piston or two either up into orbit or straight into the Earth's core. I also bring the same doom and gloom about a turbo timer, so if you spend a bunch of time boosting (who wouldn't?) and your turbos are nice and toasty (far warmer than your engine), you won't burn the bejezus out of any oil that's unlucky enough to settle in one of the turbos when you shut down. I don't know what kind of oil pump you've got, but if it's electric (hint, hint), it'll be far easier/safer to set up a turbo timer to keep it circulating for a minute or two than it would be to get the car to keep running to power a belt fed pump.

Also (I know, I'm being more of a pain in the ***), depending on the type of air sensor you're running (MAF/MAP) and it's location, it might be better to go with a set of re-circulation valves instead of the BOV's so you don't run crazy rich every time you shift. If you've got a MAP sensor either in your intake manifold or right before the throttle body, you should be good to go though.

As far as the turbos go, I'd personally go with a set of .76 AR's or .85's on a V8. Chances are, you're going to max out those .65's maybe 500-1k RPM after you get them to spin up, which is going to leave a pretty good portion of your RPM band as wasted potential. Running E85 might help a bit, but probably not enough to have any great effect. What ECU are you running?

[The Race Line]

Are you truly after a 900HP car? If so you will need to give additional thought to your gearbox selection, IMO. The 930 is a fantastic option, but your cost figures for this gearbox are a bit off I think. I have a feeling that you may be forgetting just how old these gearboxes are now, as well as how many problems they had even when they were brand new in the Porsche 917 which was substantially lighter than the GTM I think, albeit, they had a ton more tire as well. My sense is that in order to keep this gearbox alive for any duration of time, you will be looking at quite a bit more expense. Certainly more than just a billet side plate option.

A gearbox that will handle 900HP is totally possible, but I am not sure the 4 speed is your best option, at least from a durability sense. I do have some suggestions if you are open to them? Feel free to give me a call when you have time.

Best Regards, and happy building to all.

Erik Johnson
The Race Line
(970) 344-7761 phone

[Kalstar]

First and foremost, I'd second, third and fourth what wallace said about the oil cooler, your turbos are, by far, the hottest things in your engine bay. In addition, I don't think your list included a boost controller of any sort, preferably one that'll cut your boost down to 5 psi or so the moment it detects detonation so you don't end up sending a piston or two either up into orbit or straight into the Earth's core. I also bring the same doom and gloom about a turbo timer, so if you spend a bunch of time boosting (who wouldn't?) and your turbos are nice and toasty (far warmer than your engine), you won't burn the bejezus out of any oil that's unlucky enough to settle in one of the turbos when you shut down. I don't know what kind of oil pump you've got, but if it's electric (hint, hint), it'll be far easier/safer to set up a turbo timer to keep it circulating for a minute or two than it would be to get the car to keep running to power a belt fed pump.

Also (I know, I'm being more of a pain in the ***), depending on the type of air sensor you're running (MAF/MAP) and it's location, it might be better to go with a set of re-circulation valves instead of the BOV's so you don't run crazy rich every time you shift. If you've got a MAP sensor either in your intake manifold or right before the throttle body, you should be good to go though.

As far as the turbos go, I'd personally go with a set of .76 AR's or .85's on a V8. Chances are, you're going to max out those .65's maybe 500-1k RPM after you get them to spin up, which is going to leave a pretty good portion of your RPM band as wasted potential. Running E85 might help a bit, but probably not enough to have any great effect. What ECU are you running?

The ECU and MAF are both GM stock units. The MAF is about 3 inches in front of the TB. I have an STS oil pump (unused) from another project that I ended up going with a supercharger instead of remote turbo. I was planning to use that. I was looking into boost controllers but I was figuring that could be added later. My initial goal is to run low boost (6-8psi) and turn it up as I get used to the car with the new power. I heard the same thing about the low hot side. The Hy35 is from a 5.9L cummins so I figured it would be a good turbo in the 2800-4500 range. The chart I was playing with (truthfully do not know how to read it) showed a peak output at 5350rpm.

Eric, I plan to run the car in the 500whp range for some time (575 crank). Will my G50 handle that till the switch over? If not what will the trans hold (I will not hold you to it if I pop it)? I will not turn the boost up for a while. When I do, I know I will need the new trans. As you can see I like to reinvent what I am doing about every 2 years. That said I will occasionally turn up the boost, especially if the SL-C "friendly" race ever materializes. I will have a few tunes stored on a tablet and reflash as needed. On the 930, what is the RPM at 75mph in 4th? What is the top speed?

Any advise is welcomed and appreciated!

[ExtraTitanian]

Any updates on this?

[dhanisch]

Yeah, I'm still knee deep in my twin turbo upgrades. I'd be interested to hear of any progress or challenges along the way as well.

[Stage7]

Fuzzy!! You little sneak!! Just joking... Interesting choice on the turbos. What pistons are you going with? Are you going with traction control or a boost by gear solution?

[Kalstar]

All parts are here. My work schedule has been crazy and time has not been on my side. I have spent some time buttoning up loose ends on the GTM (heat/belly pans/ seat belts) and ordering turbo parts. My 818 sat for almost a year until Wallace offered me a deal I could not refuse to built it (hopefully the turbo build will not fall to the same fate of time drain). A reputable local tuner (tuned the GTM NA) will be doing the tuning (and I purchased a spare engine just incase). Two actually but one was for Nate at Factory Five. This car will be insane.

Stage...stock short block has been shown to handle over 1200 hp. I will be going with a progressive controller (boost by gear).

[tanderson1]

Would love to see some pictures. Pondering a turbo myself, I would like to see how you make all the plumbing work out.