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SD AUTOFAB
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Discussion Starter #1
just finished getting a customers twin turbo car running today, i have a 1/4 pipe to -4 feeding a tee that drops down to two -3 fittings that run through 3/16 hard line to the turbos, i then tee-d the farside turbo to plumb the oil pressure gauge in the car. I only get 20 or sounds of oil pressure at idle and 25 or so at 3000. the customer proceeds to have a heart attack that his motor has problems. I dropped the 30w break-in oil and filled it up 20w-50 to find the same readings. he goes home bummed out and i stay with my brother and do some beer powered bench racing, we disconnected the line from the bottom of the first tee and plumbed it into a gauge and found 75 pounds at idle. So i guess my question is, do i need restrictors or what?...see likes 50 pounds of bleed-off is excessive...or is it the location of my gauge?....anyone got any input?.....anything is greatly appreciated
 

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I would say some .125 restrictors are in order. If that motor has a standard volume pump it will drop off like that. If the turbos aren't gonna be happy with the restricted oil, a hi volume pump will be in order.
 

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SD AUTOFAB
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Discussion Starter #3
the turbos are journal bearing and its got the best oil pump TA makes for the bbb engine, its got the killer cover and all. were do i get my hands on some restrictors?...make them or?...thanks for the responce by the way
 

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I would put the oil pressure sending unit as close to block as possible. Verify that this fixes the oil pressure reading.

Then start the car with the turbo drains going into measuring cups. Allow it to run for 10 seconds. If I remember right you should get about an ounce per second per turbo. Then you can decide if you need restrictors.

You can make the restrictors out of -4 fittings and nitrous jets. Just sand the male an flare off and replace with jet.
 

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What engine is in the car? What oil pump are you using? Restricting the oil flow to the turbos is the very last thing you want to do, turbos need to oil to survive.
 

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I actually had a problem where I had so much pressure it pushed through the seals causing oil to get through the turbos, motor slowly started smoking like a freight train until I put nitrous jets in as restricters using the -4 set up like mentioned above, worked perfect.
 

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I would put the oil pressure sending unit as close to block as possible. Verify that this fixes the oil pressure reading.

Then start the car with the turbo drains going into measuring cups. Allow it to run for 10 seconds. If I remember right you should get about an ounce per second per turbo. Then you can decide if you need restrictors.

You can make the restrictors out of -4 fittings and nitrous jets. Just sand the male an flare off and replace with jet.
This^^^^ makes sense. Your problem is location of the sender. Move it to the block and you will see higher pressure. Try to avoid restricters if you can.

You should be able to run -4 to both turbos and still have good oil pressure. I ran 3/16 hard line to a turbo once and burned it up after 40-50 passes. On teardown you could see heat in the shaft and burned oil in the housing. I feel this was from too little flow. I switched to bigger line and no restrictors and turbo has been very happy.
 

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yes the sender needs to be first, you need to know the pressure in the engine. i always use -3 feeds. depending on the turbo's used, what turbos?
 

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remember its not just pressure its volume you need also. more oil you can get to them without issues the better to help cool them down
 

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SD AUTOFAB
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Discussion Starter #14
im gonna move the location of the gauge and see if ive got a false low reading, the oiling system is hydraulic, seems like the system is only as good as its biggest leak. also talked to ta performance yesterday and got the run down on the oil pump and cover, they use a completely stock pump that has basically been blueprinted to help oil flow. their cover has large and smooth flowing orfices for the oil to flow through. i found out they intentianally like to run the pressure low due to the deflection of the distrbutor drive off the front of the cam. they told me excessive pressure for a street bbb wears on the front cam bearing and wrenches pretty good on a some what marginal oil pump driveshaft. it has an external adjustment and i can change the springs out to boost higher rpm oil pressure. ive basically got a stock volume and pressure pump.
 

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I had the same situation a few years back.
You can't hook the gauge to the same T as the turbo feed lines.
It WILL be an incorrect low reading.
Hook the gauge up somewhere closer to the oil pump.

The turbo's should have oil restrictors in the feed line fittings. The one's I got from Bullseye have the restrictor built into the feed line fitting and it's .078 ID.
Too much oil and it can overwhelm the piston ring seals inside the turbos and come out the down pipe or go into the compressor housing.
 

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SD AUTOFAB
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Discussion Starter #16
I had the same situation a few years back.
You can't hook the gauge to the same T as the turbo feed lines.
It WILL be an incorrect low reading.
Hook the gauge up somewhere closer to the oil pump.

The turbo's should have oil restrictors in the feed line fittings. The one's I got from Bullseye have the restrictor built into the feed line fitting and it's .078 ID.
Too much oil and it can overwhelm the piston ring seals inside the turbos and come out the down pipe or go into the compressor housing.
your abosolutely correct, i built a tee from the side of the block from 1/4 pipe, has a straight -4 fitting out the top side that runs to the gauge, then a -4 line from the side of the 1/4 pipe tee to a -4 to -3 to -3 feed block then -3 lines to each turbo. the inside diameter of my -3 to 1/8 fittings is about .125, seems like a decent size according to what ive read on other peoples combos. fired the motor has 65 pounds of oil pressure at idle and builds to 85 at 2500, this is cold with 20w50 oil in it. thanks for all the good posts guys! the customer is stoked and i learned a good lesson about where to plumb the gauge
 
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