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Did anyone else's twin cam conversion fall on its face?

G

gpzTurbo

New member
Joined
Dec 4, 2013
Location
South Joisey
Hi
I have a 93 940T with stock turbo , stock ecu, and stock injectors.
i drank the KoolAid a few yrs ago and jumped in with both feet but without a proper plan. I bought the parts, borrowed the jig, broke out the tools, enlisted the help of a mechanic-friend, and went to town all full of piss and vinegar.
https://drive.google.com/file/d/13bOuEAy9FcvqjI8OLd9xgCiCIz7-k-9L/view?usp=sharing
I ruined the car.
It ran so well as a slightly tweaked 8v car I should've left it alone. We finished the head swap, drove it down the road, it came to full boost immediately, then fell on its face .
I asked questions at the time but no one had a solid definitive answer about where to start or what I did wrong.
With a few health issues now I am finishing all of life's unfinished projects or getting rid of them. I'm hoping there's more of a "formula" now.

I will put a small amount of effort into making the conversion work before I yank the powertrain out of the donor car I just purchased yesterday , put it all back to a happy 8v setup, and sell/scrap the rest.

Maybe you'll say helpful things (all of which may start with "you're an idiot") like :
- that setup was never supposed to go with the stock turbo dummy! you have to upgrade to a larger unit
or
- you can run that setup with the stock turbo but the original injectors are way too small dummy!
or
- that whole LH engine management will never work with what you're doing, Idiot.

An ultimately dreamy response to hear would be "that sh!t should've been fun as hell. you just overlooked something simple. go back and triple check your cam timing" (or something similar)
 
hi. I'm putting this car back on the road. I'm going to fix it one way or another.
and now i'm trying to remember events from a few years ago while fighting memory issues, lol

it runs out of juice before the top end
the car came to full boost (11 psi) immediately then just seemingly would not make more power, or at least not incrementally so as you'd expect. It "fell on its face" is the best way I can describe it.
the car was slower.

It made me wonder if the larger head simply flows too much for the small turbo. I'm hoping others with 16v conversion experience chime in with whether or not they had success keeping original turbo

btw I'd love to see your Grand Nat'l. I never had one but I did have a well tuned Syclone that ran 11's.
 
What ECU are you using? What are the AFR's when it seems to stop making power? Double/triple checked cam timing (with a verified TDC, not trusting the front pulley mark)?

I'd assume you're using stock 16V car cams, which are pretty good. They're no tractor cams like the 8V T cam is.
 
if you're still running the 13c, that could do it as well, that's waaay too small for a 16v
 
I'm in your neck of the woods and would be happy to take a peek at it if that would help.
 
I'm gonna agree and say more turbo needed, especially with a head that actually flows.
 
stock ecu with stock chips and original injectors. No Wideband but i remember it didn't ping.
I've since gone through a divorce, dealt with health issues, and haven't found the lostartof chips I purchased a few yrs ago .

740atl - thank you! the car sat too long now, i just finished repairing two motorcycles , finished a v8 960 wagon, then sold two other unused vehicles and am getting the L98 vette ready to sell along with the M1009 Blazer.
I'm bringing this 940 back as a keeper. I know we originally double checked cam timing, I will triple check it then PM you when appropriate as a last ditch effort to save the 16v.
Are you running a similar setup?
 
Describe what it does better. Does the power just sort of plateau early and then trail off, or does the motor cut out?

I'd suggest a standalone ECU and a WB, you're working fairly blind with a stock ECU and an ear listening for pinging.
 
blkaplan said:
13c + 16v = NOPE
Click to expand...

I hear you!
(and she says I never listen)


IF this is the case , and I do have a GT28R on the shelf, do you guys have a solid proven formula for the upgrade as far as fueling it? Will just an injector swap and fuel pressure adjustment do it or am I screwing with aftermarket management?
 
Something like Megasquirt allows you do see exactly what's going on, and change any aspect of it you need to, or want to.

Stock chips are black box, unless you buy the tools to tinker with them, and even then, they're not as easy to mess with.
 
gpzTurbo said:
stock ecu with stock chips and original injectors. No Wideband but i remember it didn't ping.
Click to expand...
When you say "stock ecu", do you mean stock 8v or stock 16v ecu?
Edit: Read your old thread and you are using LH2.4 computers from a turbo 940t. The timing maps are too aggressive and they probably won't add enough fuel. I'd stop driving the car until you can get some proper chips ion it, or you get a stand alone setup.

Original injectors for what engine and ecu combination?
Edit: Looks like stock 8v turbo injectors. Yeah, you're going to need more injector than that.

gpzTurbo said:
IF this is the case , and I do have a GT28R on the shelf, do you guys have a solid proven formula for the upgrade as far as fueling it? Will just an injector swap and fuel pressure adjustment do it or am I screwing with aftermarket management?
Click to expand...

My guess is that GT28 turbo is going to be way too small. Is it a real Garrett or a clone?
I don't know what your CR is, what your power goals are, or what your drivability goals are. This makes it a bit difficult to suggest anything...

Edit: Looks like you keep mentioning boost pressure, but what you need to understand is that a turbo moves a mass of air at a given pressure. 10psi on an 8v with a 13c and 10psi on a 16v with a 13c are DRASTICALLY different mass air flow requirements. With a 16v, a 13c probably can't even make 7psi at redline under load. The exhaust manifold pressure would also be about 2-3X that at least. All this to say, you need at least a mid frame or large t4/t3 turbo with a 0.63 or larger exhaust AR.
 
Last edited:
What sort of exhaust manifold is that 13c using on the 16V? Stock 8V manifold on an adapter or something else?

What sort of intake manifold?
 
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