lmt0705

iTrader: (7)

i just looked at a log from last year when i running twin 6766s and my mat got up near 170 then too.

kingtal0n

iTrader: (1)

well for starters a pressure test might reveal a leak somewhere. I am under the impression you did a pressure test to 30psi, since you run 30psi you need to test to 30psi. I forgot if you did that or not, but it is mandatory for all setups to pressure test to the boost pressure you run.

Next, the turbine wheel and part of the compressor wheel is invisible from the outside. Maybe one of them is torn apart. Do they spin the same speed when the engine is at idle? did you ever check the speed increase during a slight neutral rev? They should pretty much be even. One that barely moves compared to the other is a sign something is different.

pressure leaks and hidden wheel conditions aside, one of the wastegates (I think this was suggested also) could be hanging open, leaking, or have a part missing. If a gate isn't shut proper the wheel won't spin right.

lmt0705

iTrader: (7)

I did a pressure test, not to 30psi though. I'll check to see how they spin in the morning. I did a smoke test on my hotside and found no leaks. It makes boost, just takes a while to get there and does not make the power it should. I'm ripping my damn hair out over this!

Dian

would be interesting to see the boost curve. what rpm range does the engine stay in?

lmt0705

iTrader: (7)

3800-7000 mainly

a05c

How much timing is in it before it comes up on boost and when it makes ~1psi?

What converter is in it? What stator is in the converter?

Dian

at a pressure ratio of 2.2 (assuming 5 psi through cooler and 65% adiabatic efficiency) the at increase should be around 175°c (293 x ((2.2^0.283)-1)/0.65). the cooler usually removes 80% of that yielding delta t of 35°c. i asumed ambient of 20° so we get 55°c charge temp (131°F). thats ideal. somehow you start out at 114°F? so 174°c is not even bad.

but im not understanding the situation very well. you talk about excessive back pressure in the firs post. then in post 31 you present a ratio of 1.3 max, which is excellent. i would even say that is not enough, thats why the spool is slow.

as to choking on the turbine side, yes, its not good, but will only mediate the power increase from more charge pressure. i once had a car with a ratio of 3. it still responded to more boost, but lazyly. we got rid of the 1 bar drop through cooler and put a decent exhaust on. the turbo died on the first pass.

op is seeing the boost. its there, disregarding possible leaks, wastegate problems and whatever else, its there, so the engine has to make more power. i would suspect a measurement problem.

edit: as the loggs got checked in post 37, i assume there is not something stupid going on with fuel or timing. and btw, how do you know how much power your making? you took it to the track and it was not faster? slow spool maybe? boost curve, as ment. above.

lmt0705

iTrader: (7)

The only data I had last week was a street pass where the tires broke loose quickly, that's when I saw the 2/1 bp. I got to the track Tuesday to get some better data and it was consistent across 4 passes.

lmt0705

iTrader: (7)

I have a boost builder table enabled holding it at 10 degrees while on the transbrake. As soon as I release the button it commands 23.5 degrees at 4000 rpm then slowly ramps down as boost increases to a low of around 19 degrees at 27psi. It's very slow spooling on the dyno and street where the boost builder is not enabled. My data log started recording when I went wot. At that point at 910rpm timing is 28 degrees and climbs to a max of 35.3 at 2350rpm. I don't see 1psi of boost till 3340 and 32 degrees of timing. It takes 1.452 seconds to make 1 psi of boost

lmt0705

iTrader: (7)

What do you mean by a measurement problem? I just went out and started the car, both turbos seem to spin equally at idle and when revving

Dian

i was thinking that if the engine (from memory now) sees a good backpressure at 18 psi and you increase boost to 27 psi with even lower backpressure without making more power, that it all just doesnt add up. its impossible. more boost, more torque. thats it. regardless of backpressure.

unless:

- you pulled too much timing with higher boost
- your seeing knock retard
- iat retard
- burst retard
- are flodding the engine
- have some mechanical problem with the exhaust
- throttlebody is playing tricks on you
- trans is slipping (what do you logg tis, tos, tc slip?)

you have to know boost before cooler. do you have a spare boost sensor? how are gates hooked up? try the signal before cooler. if you spin the compressor wheels with a finger, how long do they move?

as to the original question: low backpressure, slow spool. i understand your not building boost before take off? did you logg g-force?

Dian

good info, steve. last time i looked (its been a while) you had to dish out three grand for that. european prices, though.

lmt0705

iTrader: (7)

knock sensors are turned off, it pulled 1 degree of timing from the iat over 160 degrees, converter slippage just doing the math is around 15-17% depending on how much boost i run

lmt0705

iTrader: (7)

on the dyno at 14psi my fuel consumption was 680lbs and made 850, at 27psi and 975lbs the car made 1091 rwhp. i talked to my converter guy, he told me 1/8 mile is not good data on converter slippage and i need 1/4 mile data to verify

lmt0705

iTrader: (7)

i had 1 quarter mile pass logged, slippage was only 6.5% so i guess he was right

stevieturbo

Oddly, even in the UK TD have them at a sensible price....well they list them, seems maybe do not stock them. My covers have no inputs, or I'd love to have a pair of them myself !

http://www.turbodynamics.co.uk/shop/...it-p-4055.html

In cases like this, it would give invaluable data.

Also...the OP is giving MAP/EMAP data....is this for a single side, or are both units operating within the same range at all times ? Or do they differ ?

Spool maybe sounds strange....especially when another user on the forum was claiming unbelievably fast spool with the same turbos, but on a 5.3 I think they had ?

Intercooler is a thought...but also a cheap/easy one to test.

lmt0705

iTrader: (7)

That is one side

sbcgenII

iTrader: (1)

What compression ratio? What fuel? If something isn't out of wack with those then I say you have a leak in the cold side or Intake manifold.

kingtal0n

iTrader: (1)

I have no idea if this would work, but it occurred to me as a test that would be easy to setup (if the pressure test is good). Can we remove the spring from one of the gates to prevent that turbo from working, and run the engine from just the other turbo purposefully? Obviously reduce boost pressure so the motor doesn't outflow it on the map. Then you could repeat the test with the other turbo and compare the data. If one of them is showing wild out of place data like a skyrocketing IAT or big difference in backpressure or slower spool character it would point to that side as a problem.

lmt0705

iTrader: (7)

9.7/1 e85