Hi guys and (girls if any),

As you can see I'm a newbie here. Recently my best friend put a turbocharger
on his 120Y A12 with blow through carb setup. He doesn't have internet access so I want to try to help him and post his problem here. I'm in no where familiar with datsun car or also carb setup, but I'm willing to learn new things just to help him so he can enjoy his car.


Spec:
pajero td04-09 turbo
blowthrough carb setup
boost 0.3 bar
NO engine mods at all.. none.. nada...

Problem & symptoms:
1st and 2nd gear got power. NO problem at all.

but when in 3rd,4th,5th , it has no power at all. The car hesitates a little with a pop "pfftsh" sounds coming from the carb I think. It sounds like to air being kick back through the carb? I'm not sure.

I look at the boost gauge when in 3rd gear, It got boost but fluctuates and not stable like in 1st and 2nd gear.

He said he tried to adjust (add more fuel) but the problem still occurs.
He has no fuel pressure regulator. All stock as far as I know.

I know his car is far from being complete, but can you guys (or girls if any) guide us the right way on how to solve this issue? What could be the cause of this thing to happen?

Some pics of his setup if its help (click on the link)
http://img30.imageshack.us/img30/3235/30012010205.jpg
http://img718.imageshack.us/img718/1999/30012010206.jpg

If any extra infos needed, I will contact him and post it here.
Hope someone here could help.
Thank you.

Quote:

Well one thing I can tell you is that needs fixing ASAP. You'll need a rising-rate FPR to ensure the fuel pressure is always higher than boost pressure. You're running about 4 psi yeah? That's still enough to overcome the 2.5-ish psi that the standard fuel pump runs on. Speaking of which, you'll need to get a higher pressure pump along with the FPR if you're running the stock item :)

Hi,

It sounds like a lean sneeze to me. Im not that familiar with blow through, but he might have to run a higher pressure fuel pump with a manifold pressure referenced pressure reg. The vent in the float bowl might have to be referenced to manifold pressure aswell. Thats one of the reasons people box the carb in.

The engine wont last long if its running lean. I`d recommend some dyno time or at least get hold of a wide band EGO sensor and run conservitive ign timing. until he gets it to a dyno.

EDIT, ya just beat me to it Spraycanman.

You can get around needing a rising rate fuel pressure reg by having a second pump with higher pressure triggered by a hobbs switch. But the RR FPR is the best bet. He's going to need a carb pressure one too. Most of the ones I see for sale are for EFI pressures.

thanks for the quick replies guys.

- Yeah I agree he needs FPR. Which one you recommend from this aeromotive carburated regulator catalog? or any other brands do you recommend?
http://aeromotiveinc.com/products-page/regulators/carbureted-regulators/

-I remember he said hopefully he can boost 0.6 bar max because of the stock condition. So what's the base pressure should be set to?

- About fuel pump: Does a used rx-7 fd3s fuel pump will be sufficient enough?

- About tuning: He has this Innovate LM-1 wideband with the tail sniffer he bought cheap from local auction. So, I think he could monitor his AFR? What would be the target AFR for his setup?

Anything else needed attention?

Thanks.