A/Rs and CCs (turbos)
Posted: May 4th, 2012, 5:00 pm
Now that I have my Yugo 1500 turbo running sweet, there is still something to address. The spool up on my turbo has never been ideal compared to the Volvo 240 T3 I have on my Spider. The T3 on my 2 liter Spider will produce 7 lbs of boost as low as 3K rpms at full throttle with more boost on tap if I wanted to run more than that. So it seems to be sized perfect for that engine.
Because 1500s (and turbocharged at that ) are rare on this side of the Atlantic I had to do the best I could do. I sourced a T25 from a 2.1 liter 1991 Saab 9000. I'm struggling to make boost and I wonder if the turbo is simply too big for this engine.
By the way I have no intercooler on this engine and this is a blow through carb system.
I've been trying to find a descent turbo calculator with no luck. So I was hoping someone could tell me from these specs if this turbo is too large for my engine.
Garrett TB2529 (saab 9000)
50trim
.48 A/R (cold side)
60trim
.48 A/R (hot side)
My Yugo is a four speed. It won't produce boost in 1st or 2nd gear. In 3rd gear it will produce 5 lbs fairly quick at 3K rpms under wide open throttle, then seems to stall until I reach 6K then it will produce 6 to 7 lbs. In 4th gear I can't get it to produce any more than 3 lbs. seems no matter what condition. Even when going up hills with the engine under a heavy load.
When I initially set this engine up I found there was a 2 lbs pressure drop across the venturis. Or I just have a bad air leak between the turbo and carb bonnet. Saabs use an APC system and the wastegates are set to open at 5 lbs. I was seeing 3 lbs at the intake manifold.
So I plumbed in a mechanical boost controller. The one that uses a spring and ball bearing that blocks the reference signal to the wastegate then opens all of a sudden until whatever it's set at.
I have moved the boost reference signal from the compressor to the hose going to the boost guage off the intake manifold so the wastegate sees "real boost". Then reset the boost controller per directions. No difference.
Then I wrapped some duct tape around the holes on my blow off valve just to see if it was leaking and bleeding off pressure. Still no difference.
Two other tests I was going to perform was to disconnect the hose going to the wastegate to see if there is some issue with the boost controller and see what sort of boost I can get without a wastegate.
The other test was to connect the boost guage directly to the compressor wheel to see what sort of pressure directly at the turbo.
The other day I pulled the air cleaner off the turbo and spun the compressor with my finger to see if the bearings were starting to seize up. It moves freely, no shaft wobble and no oil in the compressor housing. So I beleive the turbo is OK.
I'm starting to wonder if no matter what 3 lbs of boost in top gear is all this turbo can possible produce and I'm going to have to swap out the turbo to get the boost I'm looking for.
Something else to consider. I used the Saab 9000 downpipe because it had a flared end on it. I beleive it's around 2.5" in diameter. Eventually it reduces down to around 1.25" at the tail pipe (factory exhaust). I'm wondering if I'm lacking enough back pressure. I've heard turbos need some back pressure to function properly. Typically people will tell you the bigger the exhaust the better but I've also heard that is not always true.
Thanks!
Because 1500s (and turbocharged at that ) are rare on this side of the Atlantic I had to do the best I could do. I sourced a T25 from a 2.1 liter 1991 Saab 9000. I'm struggling to make boost and I wonder if the turbo is simply too big for this engine.
By the way I have no intercooler on this engine and this is a blow through carb system.
I've been trying to find a descent turbo calculator with no luck. So I was hoping someone could tell me from these specs if this turbo is too large for my engine.
Garrett TB2529 (saab 9000)
50trim
.48 A/R (cold side)
60trim
.48 A/R (hot side)
My Yugo is a four speed. It won't produce boost in 1st or 2nd gear. In 3rd gear it will produce 5 lbs fairly quick at 3K rpms under wide open throttle, then seems to stall until I reach 6K then it will produce 6 to 7 lbs. In 4th gear I can't get it to produce any more than 3 lbs. seems no matter what condition. Even when going up hills with the engine under a heavy load.
When I initially set this engine up I found there was a 2 lbs pressure drop across the venturis. Or I just have a bad air leak between the turbo and carb bonnet. Saabs use an APC system and the wastegates are set to open at 5 lbs. I was seeing 3 lbs at the intake manifold.
So I plumbed in a mechanical boost controller. The one that uses a spring and ball bearing that blocks the reference signal to the wastegate then opens all of a sudden until whatever it's set at.
I have moved the boost reference signal from the compressor to the hose going to the boost guage off the intake manifold so the wastegate sees "real boost". Then reset the boost controller per directions. No difference.
Then I wrapped some duct tape around the holes on my blow off valve just to see if it was leaking and bleeding off pressure. Still no difference.
Two other tests I was going to perform was to disconnect the hose going to the wastegate to see if there is some issue with the boost controller and see what sort of boost I can get without a wastegate.
The other test was to connect the boost guage directly to the compressor wheel to see what sort of pressure directly at the turbo.
The other day I pulled the air cleaner off the turbo and spun the compressor with my finger to see if the bearings were starting to seize up. It moves freely, no shaft wobble and no oil in the compressor housing. So I beleive the turbo is OK.
I'm starting to wonder if no matter what 3 lbs of boost in top gear is all this turbo can possible produce and I'm going to have to swap out the turbo to get the boost I'm looking for.
Something else to consider. I used the Saab 9000 downpipe because it had a flared end on it. I beleive it's around 2.5" in diameter. Eventually it reduces down to around 1.25" at the tail pipe (factory exhaust). I'm wondering if I'm lacking enough back pressure. I've heard turbos need some back pressure to function properly. Typically people will tell you the bigger the exhaust the better but I've also heard that is not always true.
Thanks!