North American Turbocoupe Organization



Got the Gillis Valve on tonight, boost wont hold steady, is the turbo too small?
Speeds8erM-1 Offline
Member
#1
I got the Gillis Valve on tonight, went and drove it, wasnt hitting much boost but didnt have to wait on the stock boost control anymore. I adjusted it, still didnt hit much, finally got it to where it spikes to 17 PSI maybe 16 PSI, then falls down. It only hits like 15 PSI in first and second, spikes to 17 might be 16 in third, holds there for a second, falls down in the 4000-5000 RPM's range, shift to fourth, hits 17 PSI again, might only be 16, stock gauge sucks, RPM's go up it falls down to 15.

I dont see what the point in having the valve is, if the boost only goes up a little, for a second, in a couple gears.

The car is also hesitating a little up top, it was doing this before but is a little worse now. When you get into third and fourth, with some RPM's, it starts hesitating, I need to check fuel pressure but the gauge I can borrow has a fitting for a GM. Could this be the fuel pump not keeping up, I dont see how, car is pretty much stock?

It is pulling harder, except for the hesitation. It's on there EXACTLY like the directions said. Is the turbo just too small? It really only pulls harder in the mid range though because the boost just dosent stay high enough in the upper RPM's. I was getting 14 PSI before the Gillis Valve. Is the stock exhaust choking it maybe?

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1989 Mustang LX Hatchback, Black, 5 Speed, 306, TRW's, F303, 3.55's, alot more
1988 Mustang GT, Black, 5 Speed, Explorer Intake, 93 Cobra Cam, 3.55's, alot more
1988 Thunderbird Turbo Coupe, Silver 5 Speed, K&N
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Speeds8erM-1 Offline
Member
#2
I will also mention, I used the search and couldnt find anything exactly like my problem. [Image: smile.gif]
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Pete D Offline
Administrator
#3
If it's hesitating them there is an uneven supply in the exhaust spinning the turbo. That might be part of your spiking problem.

I agree you need to check fuel pressure. The stock pump were marginal at best and tend to get weaker with age.

It's not unusual to get less boost in 1st and 2nd. The car isn't in that gear long enough to really build it higher and the engine doesn't see the load it does in higher gears.
Pete Dunham


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Speeds8erM-1 Offline
Member
#4
Could you elaborate a little more on the uneven exhaust spinning the turbo? [Image: smile.gif] It has been doing it, it has just gotten a little worse with more boost. I know it wont build much boost in first and second because not much load with the 4 something first gear but d@mn, I was hoping it would add more than 1 PSI. [Image: smile.gif]

It's not the original fuel pump but it is a stock pump, I hope it's not the problem. I dont hear any pinging, it does feel like a hit a rev limiter kind of, when I spin and it revs to 5200-5400 in first gear, it's not quite the same feeling as the hesitation in the other gears though. I am going to drive it again and see how it feels, the Gillis Valve dosent have many more threads left either.
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Speeds8erM-1 Offline
Member
#5
I turned the boost up some more and drove it. It will now hit 17 and fall off to 15-16, I ran it to 4600 in fifth and it didnt turn the overboost buzzer on but I was cruising in 5th, making the boost jump up by hitting it and letting off, it turned the buzzer on one time. It is still hesitating, it just feels like it isnt pulling that hard in the 4000-5200 range.
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Thunderbird88 Offline
Member
#6
If it's hesitating then u might want to try putting some NKG V-groove plugs in. Mine was bucking and hesitating too until I put the plugs in. For about $1.70 apiece, that's a cheap start. I was lucky enuff to have my problem end with the plugs.
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jabobia Offline
Member
#7
is there a bleed device built into the gillis?...i had to drill a bleed hole in my controller because over 14psi it would spike high then come back to 15psi...pressure gets trapped between the ball and the WGA causing it to stick open and slowly close...anything around 9psi will open the WGA so 17psi trapped in there will do the trick

heres a link straight from the gillis site on adding a check-valve, which if theres no bleed in the gillis, would solve the problem :
http://www.boostvalve.com/tech/checkvalve.html

-james

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87 TurboCoupe - 5spd
87 Thunderbird TurboCoupe - 2.3T, T5, 3.55L - K&N, 18psi - 16.14@88mph(2.37 60')
88 Thunderbird Sport - 5.0SO, AOD, 2.73L - 16.77@82mph(2.39 60')
www.cardomain.com/id/jabobia
jabobia.com
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Pete D Offline
Administrator
#8
There is a bleed hole in the Gillis.
Pete Dunham


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Speeds8erM-1 Offline
Member
#9
It's already got NGK's in it.

Pete, could you explain a little more about the uneven exhaust supply? [Image: smile.gif]
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natmac3 Offline
Administrator
#10
If you're still running the stock boost gauge, you may want to invest in a better one... The readings may be anywhere from close to way off, like mine was...
1987tc
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