'Judas' Audi Rs6 - 383 twin turbo, EGT reading confirmation.
05-02-2014, 05:54 PM
#1
Staging Lane
Thread Starter
'Judas' Audi Rs6 - 383 twin turbo, EGT reading confirmation. Hi All,
I don't post here much but I have a question I figured you guys and gals could help with.
For those unfamiliar with my project (one of them) here are the basic specs and link to my intro post
https://ls1tech.com/forums/conversio...ect-judas.html
2003 audi RS6
GM LS1 conversion retaining audi AWD with built 6spd 01E transmission and Clutchmasters FX850 twin disc clutch.
LS1 383 SCAT stroker, AFR 230 mongoose heads, Fast 92 intake, Custom grind comp cams turbo cam, roller rockers, 1000cc injector Dynamics injectors.
Dual rear mount Precision 6266 ceramic ball bearing turbos with rear mount intercoolers.
Custom headers with 4" collector by drivers side rear of head (crossover 3" pipe from passenger bank). 4" pipe to rear where it splits to 2x 2.5" feed pipes for the turbos (about 18" long each) Whole system is ceramic coated and wrapped.
3" feed pipe from dual rear intercoolers to custom CF cobra head into GM 100mm E-throttle body.
We just swapped in the precision turbos as we found the 3076's (.68AR) we had on initially were undersized and would run out of steam at about 5500rpm. we did a backpressure test and were seeing a deltaP of over 4:1 (10psi intake pressure = 45ps exhaust back pressure) We were also seeing what we considdered crazy high EGT readings (EZGT probe is in collector at headers where both banks merge to the single 4" pipe, approx 6" from rear most drivers side primary) We were seeing 8-900 idle, 1400 cruise and up to 1550 full pull at 13psi on the dyno)
So I just got done at the dyno with the 6266's which are .82AR Vband in and out.
Our EGT's didnt really drop as much as I expected. We are still seeing idle of 800, cruise *(load at 65mph 3-4psi boost) 1200-1300 and 1450 at full pull (14psi boost)
The good news is these turbos dont run out of steam, with E-boost control we can hold whatever PSI we want wherever we want. The bad news is they spool late, we see 1psi by 4K, 10psi by 4700 ish and 14 psi by 5200 (compared to the old turbos which were making 13psi by 3500rpm)
Excuse the rambling intoridcution, just a bit more to get all the facts out before my questions.....
I suspected the PLX EGT was off, so I added a second EGT probe about an inch from the first and logged with an external logger and they are within 100F of each other.
I just did a repeat of the exhaust back pressure test and the results are good. Anlyran to WG spring pressure of 7.9psi, at I saw 19psi exhasut back pressure, so DeltaP is now 2.4, which I feel is acceptable for this motor turbo configuration.
so the questions are;
1) Typical EGT readings for a boosted LS, reading in the collector pre turbo (I know they will vary based on specific setup) Does anyone have a good read on typical EGT readings for idle, cruise and full boost pull?
I have been reading up online and it seems my numbers are typical which surprises me as I am used to numbers being 2-400F lower in the euro cars I build.
2) Exhaust back pressure, what are people with similar setups (front or rear mount turbo systems) seeing? typically I see 2- 2.5:1 delta P for front mount turbo setups. Sometimes lower but rarely.
For those who are interested, on the old turbos we made 680AWHP/700TQ at 13.8psi
On the new 6266's we called it early due to EGT concerns so on a partial pull to 5.5k rpm we saw 720WHP/740WTQ at 13.8psi.
Our goal is 1000AWHP/TQ at under 20psi, then back it down to 15-18psi for DD use.
Video of the old turbos, didnt get ony of the new turbos yet. (theres a bunch more videos on my youtube channel.
I don't post here much but I have a question I figured you guys and gals could help with.
For those unfamiliar with my project (one of them) here are the basic specs and link to my intro post
https://ls1tech.com/forums/conversio...ect-judas.html
2003 audi RS6
GM LS1 conversion retaining audi AWD with built 6spd 01E transmission and Clutchmasters FX850 twin disc clutch.
LS1 383 SCAT stroker, AFR 230 mongoose heads, Fast 92 intake, Custom grind comp cams turbo cam, roller rockers, 1000cc injector Dynamics injectors.
Dual rear mount Precision 6266 ceramic ball bearing turbos with rear mount intercoolers.
Custom headers with 4" collector by drivers side rear of head (crossover 3" pipe from passenger bank). 4" pipe to rear where it splits to 2x 2.5" feed pipes for the turbos (about 18" long each) Whole system is ceramic coated and wrapped.
3" feed pipe from dual rear intercoolers to custom CF cobra head into GM 100mm E-throttle body.
We just swapped in the precision turbos as we found the 3076's (.68AR) we had on initially were undersized and would run out of steam at about 5500rpm. we did a backpressure test and were seeing a deltaP of over 4:1 (10psi intake pressure = 45ps exhaust back pressure) We were also seeing what we considdered crazy high EGT readings (EZGT probe is in collector at headers where both banks merge to the single 4" pipe, approx 6" from rear most drivers side primary) We were seeing 8-900 idle, 1400 cruise and up to 1550 full pull at 13psi on the dyno)
So I just got done at the dyno with the 6266's which are .82AR Vband in and out.
Our EGT's didnt really drop as much as I expected. We are still seeing idle of 800, cruise *(load at 65mph 3-4psi boost) 1200-1300 and 1450 at full pull (14psi boost)
The good news is these turbos dont run out of steam, with E-boost control we can hold whatever PSI we want wherever we want. The bad news is they spool late, we see 1psi by 4K, 10psi by 4700 ish and 14 psi by 5200 (compared to the old turbos which were making 13psi by 3500rpm)
Excuse the rambling intoridcution, just a bit more to get all the facts out before my questions.....
I suspected the PLX EGT was off, so I added a second EGT probe about an inch from the first and logged with an external logger and they are within 100F of each other.
I just did a repeat of the exhaust back pressure test and the results are good. Anlyran to WG spring pressure of 7.9psi, at I saw 19psi exhasut back pressure, so DeltaP is now 2.4, which I feel is acceptable for this motor turbo configuration.
so the questions are;
1) Typical EGT readings for a boosted LS, reading in the collector pre turbo (I know they will vary based on specific setup) Does anyone have a good read on typical EGT readings for idle, cruise and full boost pull?
I have been reading up online and it seems my numbers are typical which surprises me as I am used to numbers being 2-400F lower in the euro cars I build.
2) Exhaust back pressure, what are people with similar setups (front or rear mount turbo systems) seeing? typically I see 2- 2.5:1 delta P for front mount turbo setups. Sometimes lower but rarely.
For those who are interested, on the old turbos we made 680AWHP/700TQ at 13.8psi
On the new 6266's we called it early due to EGT concerns so on a partial pull to 5.5k rpm we saw 720WHP/740WTQ at 13.8psi.
Our goal is 1000AWHP/TQ at under 20psi, then back it down to 15-18psi for DD use.
Video of the old turbos, didnt get ony of the new turbos yet. (theres a bunch more videos on my youtube channel.
06-15-2014, 09:54 PM
#2
Figure anything out about egts?? I've been searching on yb haven't found anything on here. Have been working on my idle egts and can't get them under 950 cruising 1150-1200 wot 1350 so I'm right with you on pump. Would like cruising to be better but not sure if these are acceptable.
06-16-2014, 05:04 AM
#3
9 Second Club
1550 degF pre turbo on full load is by no means too hot or excessive for pump fuel.
Idle and cruise sound reasonable as well. Although how temps vary with headers and the turbos mounted so far away, not really sure.
My other query...is how much can we trust the EGT probes, when there isnt any really easy way to test them ?
I'm seeing as high as 2100degF pre turbo on mine at around 20psi. But I simply do not believe that to be accurate. But it can vary from around 1900-2100...which makes little sense.
Probe is about 3-4" from the closest exhaust valve, so a warm location anyway.
Such huge collectors, such a huge pipe from front to rear, absolutely have to be having a huge negative impact on spool.
And I'd say also combining the pipes, then splitting again would also be having a huge negative impact.
A Pair of 2" pipes would probably make a lot more sense, keep gas velocities high and divided from each bank to each turbo.
IMO 2:1 is pretty high, I'd like to see much lower than that.
Idle and cruise sound reasonable as well. Although how temps vary with headers and the turbos mounted so far away, not really sure.
My other query...is how much can we trust the EGT probes, when there isnt any really easy way to test them ?
I'm seeing as high as 2100degF pre turbo on mine at around 20psi. But I simply do not believe that to be accurate. But it can vary from around 1900-2100...which makes little sense.
Probe is about 3-4" from the closest exhaust valve, so a warm location anyway.
Such huge collectors, such a huge pipe from front to rear, absolutely have to be having a huge negative impact on spool.
And I'd say also combining the pipes, then splitting again would also be having a huge negative impact.
A Pair of 2" pipes would probably make a lot more sense, keep gas velocities high and divided from each bank to each turbo.
IMO 2:1 is pretty high, I'd like to see much lower than that.
