I came across a used LPE C5 twin turbo kit which I picked up. Initially, I thought to slap it in my daily driver coupe get it running and sell the car and make a few extra bucks. The longer I think about it the more I am curious about converting it for use with my Z06.

There are problems with this idea though.

Pros: the kit comes with Kooks primaries, an electric oil pump setup instead of the pulley driven kit, and a Treadstone IC which looks to be good up to 900+ range.

Cons: turbo size, design and space limits.

The perks are fair, but the turbos which come in the kit are old Garrett T28s which are internally wastegated to who knows what psi right now. 5psi? 9psi?

Using them on my existing 402 makes me think they would absolutely spool into boost creep because of the increased backpressure.

Upgrading the turbos presents questions for me. I don't believe I have enough space in there to run an externally wastegated turbo easily - and that is what I would prefer to do with a pair of 45mm or 50mm gates and electronic control since my geeky dream has always been to have boost-by-gear to optimize power and grip. With the Haltech in place this would absolutely be my goal.

And my goal with boost-by-gear and turbos in general would be less power and less cam until I decide I want more situationally. It's a lot of fun to run around town with 550whp on tap and have a blast while not having the same concerns for traction or corners as with 750whp. Or even to take the wind out of the turbos almost entirely and just run the car at at 440rw almost NA. But I'm probably reaching beyond my grasp here on a kit that is 20 years old and designed to be "set and forget."

I am unfamiliar with the current turbo market. Maybe there is another combo which would fit, spool faster, and handle the backpressure. Still unsure where an external wastegate might fit currently. I mean, unless I ditched the batwing pan and went with a C6 pan instead and was able to tuck it in close.

Goals: Cake, eat it, not turn into another $6-8k sinkhole. If I can get away with something from VS racing which would fit the bill and I could get a pair of turbos for under 2k.... ok maybe.... big maybe. But from where I sit currently I am not seeing how this kit would fit my interests and/or not nuke my engine in a runaway overboost scenario.

Be my devil's advocate. Convince me how I could make the kit work for the 402.

 

that kit is a smoken deal, BUT, you are right the T28 will choke off a 402 and you won't be happy.

LPE did run bigger turbos on those manifolds on the 427 cars making 850 or more hp which would be better suited for the 402

fabbing up the plumbing will be a bit of a trouble as I don't think the old silicone c5 LPE TT stuff is still available. Those turbo manifolds are beautiful though!!!

Do some searches on the LPE TT cars. I was lucky and snagged the huron kit with the 64/67 turbos which would be about right.

Not sure how big you can go on the LPE manifolds but I'll bet you will be just fine. Chris gave me one of the oil drainback pieces, I'll find it and get it shipped up to you.

Let me know if you decide to sell it, I think that stuff is worth more.

 

I definitely intend to use it. I'd prefer to have my cake and eat it too somehow with the Z, especially because I'm not seeking a 1k machine. And if I can't determine a way to make it work then it will go on another lesser street machine.

I had spotted that other post you scored but half a dayvafter you. Good score!

My focus currently is on fitment of a gtx3071 or gtx3076 without boost creep.

And I am wondering if there is anyvway to add an external wastegate, though I doubt it, and yet I won't know spacing well until it's all on a car.

So a base LS with this kit is still the safe option.

Let me know if yoi sell that other kit of yours!

 

I still have the ttix kit which is good to 1k, but I plan on using it on my 02 anniversary car after I can get the z06 huron setup built out

tough getting the drivetrain mods to hold much beyond that. Can't afford a 480le upgrade so a maxed out 4l70 will be as good as I can get

Also thought about c6 z06 stuff but the auto performs better overall and is easier to drive

keep in touch!

 

Tough decisions. And all good outcomes though!

I still think if I were to go auto and dedicated drag I'd seek out an fbody or a small truck platform and dump the 80e into it. Though I've also considered building a Tahoe into a daily with a mild cam and single top mount turbo.

 

I have been messing with one (originally 383cid twinturbo LPE) 97 C5 and it's updated with GT3076R snails. Cam has been changed and the heads are aftermarket too.
It was dyno'd 800/800 (crank hp/lbft) on a hub dyno but it didn't come easy. To get it on those numbers it needed big cutouts on pipes and it needed a perfect weather.
The main headache is heat. All the wiring looms in the engine bay have been somewhat damaged, even the brake servo gave up. The setup is so tight that air doesn't have much room to cool stuff down.
I think we took the max out of that setup. There's no room for any bigger turbos than these. It's pretty decent to drive though, the boost comes on at fairly low rpm and it's controllable.
Third 4L60 is in right now, the first two were supposed to handle 1xxx hp but gave up pretty quickly. Coan torque converter also lost splines at one point.
Not cheap, nor easy. But this is life with modified stuff.

 

It makes me wonder if an airframe under the cradle and front clip with directed vents up unto the turbo location might help with that.

For me, I've already gone fairly overboard with the DEI shields and hose covers everywhere so that would not be any additional headache. My SC combo on a maxed out V3Ti has shown 740 to 990 wheel based on fuel and rpm. I intend to run pump but am rigged to flow E85 or other.

800 is more than I can conceive of on the street. And if I could get the optimal outcome of boost/traction by gear that would be epic.

Which housing did you use? Were you able to squeeze external gates on them?

 

Waste gates were in the housings, I can't see a way to fit external ones, at least with any ground clearance. In fact I think getting past the housing from top to down would be impossible. There is no room for even tightening any oil line nuts without removing a header with the turbo and lowering those a bit.
This utilizes also those heat shield tubes around wirings but it wasn't the answer to problems. Those wires melted inside those socks too. There is a need for an air gap between the wire and the shield and it's hard to maintain.
I made thin metal shields around headers which stay a hair away from the header surface, this helped a lot and directs the hot air to certain areas. So that it won't radiate everything to death.

 

in the old days with the 5 bolt housings on the buick turbos we'd enlsage the WG housing hole and put a bigger puck on to seal it up.
thanks for posting about your 4l60 tranny experience. Seems like the these trannies even "maxes out a 1k" which isn't cheap won't hold up that well.

4th gear is a no go. Not sure which way to go there, as the 480le is just way to costly. Anyone swap in a maxed out 680le from the C6? They used to be a no go but folks have figured out the tuning and hop up parts

pretty strong box. Or the 8 spd auto out of the c7 they can really be beefed up and hold a ton. But no controller yet that I know of other than the stocker.

 

wow, the 4l65 even built to the hilt doesn't take the power. I ran 800 at the tire with my RPM built box but didn't launch hard and limited the drag strip use as they don't hold up.

The 480LE swap is WAY too expensive so I'm looking to do boost by speed and more active controll over the torq conv lockup and have to stay out of 4th.

The PG swap isn't for me either as I'm old enough my drag strip runs are behind me and I value the street manners and durability. So I'm likely to stay around 800 or so at the tire and stick with street tires (good ones, GY SC4s 305 19s) and limit the pounding on the trans. The stick TR6060 box with good dual disk might be able to handle the power better, but the auto puts it down SOOO much better and easier. Loads the turbos nicely too to cut the 60 ft times without the drama and near death experiences of rowing down the quarter trying to hook up 800 ft lbs at 3200. The little turbos just spool TOO quickly and pound the pistons with big boost a low rpms (no bueno) New strategy is to ramp the boost up more linear like the blowers too and then really charge on top end once traction is more available. spinning ain't winning and hooking up the big power and making it live ain't easy in the c5.

Tusc is right, if you build a drag car, build a drag car. My old c3 80 BB vette with the turbo 400 ran low 9s normally aspirated and was cheap. Build like a tank with full frame, modular 9 inch ford rear, spool. Car ran 9.20s and only cost me 17k. WAY cheaper route to go fast for cheap. Even with advanced scrounging, modding the vettes isn't cheap or ez.

 

As I am talking to folks and asking loads of dumb questions so I can learn, my interest is similar now in terms of a combo which will build power into upper rpms and not snap in at launch. Boost / torque / traction by gear seems attainable. And for the launch at least there are cheats out there for consistent clutch slipping such as the bang shift billy hydraulic controller.

 

fancy boost control to move max cyl pressure higher away from peak torq will make the big power live

the guys that know more than me focus on that 5-8k power band with the peak boost upstairs

keep the timing conservative at peak torq and ramp it back up just a little and make sure to avoid detonation!!

I'm hoping to get a new Nexxus or at least install my older Platinum S2000 which has been shelfware for too long

But I think a good boost controller can do the same thing cheaper and my wallet points back to e85 tuning with the stock 04 ecm

the cool engine active alerts aren't there, but again, the fancy boost controllers are smarter too now.

that Huron kit without the turbos looks great, you can buy some very nice turbos for 4k!~!!

 

Turbosmart just entered the market, but to risk a new producer at prices as high as they are asking seems ludicrous.

A pair of peaky 6466 cea gen 2 might be the ticket. But on this one i am definitely going to talk to Bret first. Not least of which because I'll want a smaller cam while accounting for cr and spooling the twins. Any cam is a boost cam.... But may as well optimize it.

Hate to say it but some turbo cams sound awkward as heck. I have had thay stoccatto Jam Cam idle in my head for three year and changing directions is oddly harder than you'd think.

 

Brent made a comment a while back that I cling to. Run a cam that allows the turbos to spool up and drive into the rpms

Once the turbos light off, they really get the car moving. I think you are onto something with the cams though. You still want to make the cam run in the rpms you want to maximize the powerband of the turbos

as long as they don't choke, they will allow the engine to rev up more, and live better too. I had a hard time with that, but it sure makes sense.

He can advise you on cam timining and indeed the turbos. I think the 64/66 would spool quickly and provide plenty of CFMs to drive the power.

The turbos are kinda like cams too. Select the turbos to be in the sweet spot of the map within the power band and desired airflow to make the power needed.

I'm going "slightly too big" on the 64/67 (well hell they were cheap). On a 5.3 engine, they will be a bit slower to spool up, but pull like a bear up top.

I'm hoping that will help me hook without having to bleed off too much low end boost and making the tubos very happy at around 7200-7500 which I hope will make for a reasonable rpms for street and still give me that wide 3500-7500 pull with emphasis on the 5500-7500 range really coming alive. Lower gears won't allow that much boost, but 3rd gear will be a hero.

Might even go back from a 3.42 to a 3.15 gear to make that 2nd and 3rd gear pull longer.

With the stick, you have a similar challenge to hook the lower gears, 3rd 4th and even 5th will pull like a bear, hooking up 1st and 2nd is a big challenge. At 800 ft lbs at 3200 rpms, low end torq is NOT an issue.

Bleeding some of it off, and allowing the car to hook is.

 

Which is exactly why when choosing a cam for a stick/turbo/street car application, low end and midrange torque from the cam means next to nothing. (No need for an early IVC to start building cylinder pressure too soon) I would instead focus on a cam that breathes better up top when exhaust backpressure is present. That usually drives an early EVO. If your cam guy isn't talking in terms of valve events (EVO, EVC, IVO, IVC), he's still living in the dark ages.

 

I was planning to call Bret on this. Lots of direct experience with turbo apps as well as customers, and he is up on the spintron induced changes Brian has been developing.

 

I need to get my z06 to Brent and have him build it. I've got so many projects ahead of it, and I'm tired of looking at it.

Brent has the right expertise for helping you and is amazing to work with

 

Bret? Absolutely. He's my brother from another mother and missing one T where I have two. And he is absolutely the guy in the know for turbo and cam setup on these engines. I was talking to him the other day and catching up but never got around to car talk as I got pulled away by my wife's attorney during a deposition prep meeting. I've been mouth breathing from the couch for two days since then with a tough cold.

 

interesting discussion. everybody is afraid of "boost creep" but its really what you want. i set up all turbo cars like that.

btw, what are GY SC4s tires? i only see some SC4 mud tire.

 

I'm not talking about boost creep,

BUT too much boost low in the RPM ranges is a hard on the equipment. Bring in the big boost higher in the rpm range past peak torq

ramp it hard from 10 psi at 4500 to whatever she'll take at 7k+ Too much boost below and at peak torq can tear things up

Bent rods, detonation, bad things. With the big v8s, you have plenty of low end, and the LS tolerates revs well