454 turbo impco 425 x2 tuning help

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storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: 454 turbo impco 425 x2 tuning help

Post by storm »

If the turbo is spooling at 2400 rpm (200 rpm higher than before the change you just made which to me is a great leap sideways if not backwards) and the engine isn't responding to it until 4000 rpm I'd suggest the build parts combination could possibly be a problem.

We know a little bit about the turbo. We can see the intake pipe is restrictive. Can you tell us what parts your engine has? Is the transmission auto or manual?
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

cardar911
Posts: 12
Joined: Sun Jul 13, 2008 1:48 am

Re: 454 turbo impco 425 x2 tuning help

Post by cardar911 »

Thanks for the responses guys!!

I had a ball valve adjustment inline the balance line before the y section. I've taken it out to check for a diffence.

It's running a 2.78 rear gear ratio and a standard turbo 400 transmission and convertor.

Very interesting the gas valves, been working on it today the car feels solid enough for dyno tuning I think.

Just wanted to check if the setup is 100% right before tuning.

Thanks again guys

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: 454 turbo impco 425 x2 tuning help

Post by storm »

cardar911 wrote:
Fri Apr 24, 2020 11:38 pm
It's running a 2.78 rear gear ratio and a standard turbo 400 transmission and convertor.
And you want 700RWHP? You'll blow it all apart unless things are beefed up.

When I asked about the combination and then specifically asked about what parts the engine has I was referring to heads, compression, cam etc etc etc. As it is you've got a slow diff which will make the engine work harder to rev so it will labour in the "doughy" zone for longer. If you were running a 3.08 (at the very least) or even better a 3.23 or 3.55 the engine will rev through the "doughy" zone much quicker. Having said that there will still be a "doughy" zone and that is what we are trying to sort out.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

cardar911
Posts: 12
Joined: Sun Jul 13, 2008 1:48 am

Re: 454 turbo impco 425 x2 tuning help

Post by cardar911 »

Stock heads, forged pistons balanced bottom end. Approx 8:5 compression ratio. Comp cam turbo/supercharger camshaft.

Yeah think rear end needs 3.2 ish

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: 454 turbo impco 425 x2 tuning help

Post by storm »

cardar911 wrote:
Sat Apr 25, 2020 1:03 am
Stock heads, forged pistons balanced bottom end. Approx 8:5 compression ratio. Comp cam turbo/supercharger camshaft.
Don't take this the wrong way but I'm done here, I can't help you with anything when the information you supply is less than basic.

Let me give you an example of the type of reply I'm looking for when I ask you questions trying to help you figure out why you have 1500 rpm of "doughy" feeling engine.
Heads are rectangular port with a matching Edelbrock Air Gap manifold, Cam is a Comp Cam with 256 degrees at 50 thou lift and 650 thou lift overall running 1.7 ratio rockers.
Or heads are oval port with etc etc etc.
The reason I ask this is big block Chevs have 3 different type of heads, rectangular oval and peanut, and 3 different valve combinations. There are hundreds of different manifolds and 1 cam manufacturers turbo cam is anothers hipo cam. Without actual specs "Stock heads, forged pistons balanced bottom end. Approx 8:5 compression ratio. Comp cam turbo/supercharger camshaft" means very little apart from you are never going to get 700 RWHP from this engine.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

cardar911
Posts: 12
Joined: Sun Jul 13, 2008 1:48 am

Re: 454 turbo impco 425 x2 tuning help

Post by cardar911 »

Update guys

I found leak in the carb the balance outlet bung was missing. Runs and starts alot better. Rev range is very smooth. Boost hits hard at 3800rpm.

After some research I think the turbo is too large and it's simply lag. I don't know exact specs of the turbo and can't find them. It's a kkr1000 t6 flange maybe 1.68ar?

Looking at gt45 1.15ar. Impco 425s love boost I think onto a good thing here!!

Cheers

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