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Guest Message by DevFuse

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horrible fuel mileage (86 Turbo)

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3 replies to this topic

#1 subiekid


    Subaru Nut

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  • Coeur d'Alene, ID

Posted 14 December 2005 - 11:53 AM

My 86' Turbo wagon is getting horrible gas mileage. It has never been great, but now I am getting like 10 MPG. The only big change that I have made is the N/A Spider intake, other than that everything is the same as before. Also I am having a huge detonation problem, I can't even run the car at anything over 10 BTDC because as soon as the boost hits, I get detonation. But the thing doesn't have anything down low with the timing set like that. Either way, the detonation problem is much higher on my list than my gas mileage. Anyway, any help would be greatly appreaciated. Thanks!

The car is:
1986 GL-10 Turbo
WRX intercooler, NOPI blowoff
straight through magnaflow exhaust
Spider intake w/K&N filter (cone)

#2 rallyruss


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  • San Jose CA

Posted 14 December 2005 - 12:23 PM

things to check.

its a hot wire maf? if so make sure the little sensing element is clean. that can cause some nasty pining/lean conditions. if its the flaper type make sure its opening smoothly. better yet get a DVOM and check the signal.

some other things.

possibly the coolant temp shorted to ground?

low fuel pressure? what presure regulator did you use when you swaped manifolds?

air leak after MAF but before turbo? look for splits in the hose lines poped off.

#3 subiekid


    Subaru Nut

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  • Coeur d'Alene, ID

Posted 14 December 2005 - 01:43 PM

It's got the flapper MAF, everything is operating smoothly there. I used the pressure regulator from the XT that the intake came off of. Whatever it is
is causing multiple things to not work right. I have the car set to stock boost right now because even if I turn it up I don't get hardly any more power. I can crank the boost to 12 or 13 pounds (and retard the timing some more) and the car wants to go but you can feel something holding it back (timing???). Sometimes you can mash it and it will pull VERY hard but only every now and then and for a short duration at that. Don't get me wrong, the car runs great and driveability is great plus it still pulls 5 times harder than stock it just feels like it wants to run much harder and it can't.

I forgot to add to my original post, I am running a carbed block so the compression is up a little.

#4 Ross


    Can't be bothered

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  • Christchurch, New Zealand

Posted 14 December 2005 - 03:53 PM

Check the vacuum advance on your distributor re the detonation - it should retard the timing under boost.

Does sound like you have a fuel problem though, like low fuel pressure..

You may not need to have your riming much further advanced than 10 deg with that carb block.

Im not surprised it doesn't feel right at 13psi with 8.7:1CR. That would be about the limit for your fuel system.

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