Dr Turbo or Jose inside please, got a tech weather/altitude turbo question
10-22-2008, 11:40 AM
#1
Dr Turbo or Jose inside please, got a tech weather/altitude turbo question I've been looking over my log files from my last track outing. I noticed an anomoly in the amount of boost i'm running. If I set the boost controller to hold 208 kpa it will hold between 205-209 (16psi) for the entire run. Looking at some video the wastegate opens 50-60' after launch (new converter on order). I tried turning up the boost to 225 kpa (18psi) and all my logs show me reaching 220-225 kpa by 6000 rpms in 1st gear, but by 7000 rpms it's tapering off to 205-209 and then stays there for the rest of the pass. On the one of the crappy videos I have I don't think the WG is even opening on the 225kpa setting. I'm waiting for some higher quality videos to make a final call on it though. My IAT's also went up about 15-20 degrees by the end of the pass with the higher boost to the 165 range (start IAT of 97) which seems like a big jump for a 2psi increase. If I turn it up over 16psi now I can see a spike in 1st gear or 2nd gear on the initial hit, but the boost drops 1-2 psi by the end of the gear. It will hold steady at 16psi and below.
In hotter weather I had been able to get 20psi out of the turbo and hold it the entire pass (with no MPH gain). The only real change to the car was eliminating the over axle piece and going straight through under the axle which eliminated about 300 degrees worth of bends and probably 2 feet of piping in a very short distance.
I know that by being rear mounted i'm losing some of the total output of the turbo, but how much output am I losing due to the thinner air? Am I reaching the compressor side choke point (too much compressor rpm)? Air consumption should be around 86lbs/min at 7000 rpms and a 2.05 pressure ratio based off my 135-136 mph trap speed and 3800lb race weight. I haven't pulled my air filter at the track, but I have done it on the dyno before and it showed a zero HP gain so I don't think it's a major restriction. I have a 4" mandrel bend feeding the turbo to a smooth 4"-5" transition.
In hotter weather I had been able to get 20psi out of the turbo and hold it the entire pass (with no MPH gain). The only real change to the car was eliminating the over axle piece and going straight through under the axle which eliminated about 300 degrees worth of bends and probably 2 feet of piping in a very short distance.
I know that by being rear mounted i'm losing some of the total output of the turbo, but how much output am I losing due to the thinner air? Am I reaching the compressor side choke point (too much compressor rpm)? Air consumption should be around 86lbs/min at 7000 rpms and a 2.05 pressure ratio based off my 135-136 mph trap speed and 3800lb race weight. I haven't pulled my air filter at the track, but I have done it on the dyno before and it showed a zero HP gain so I don't think it's a major restriction. I have a 4" mandrel bend feeding the turbo to a smooth 4"-5" transition.
Last edited by Zombie; 10-22-2008 at 01:12 PM.
10-22-2008, 12:27 PM
#2
Well, first your pressure ratio would be 2.1 for 16 psi, assuming that your ambient pressure is 14.7psi. But, because you are running in Vegas at altitude (2000ft elveation ambient ~13.66psi) your ambient pressure will be less so your pressure ratio will be higher, actually 2.18.
Also, how do you figure 86lb/min, did you base this off of a certain VE? If you assume a 82% VE for a 366CI engine at 7000RPM with 14.7psi ambient you would get 86lb/min. But, with the lower ambientpressure you would get ~90lb/min at the same VE, CI. and RPM.
From my experience when the boost tapers off at higher RPM you are either maxing out the compressor (doesnt sound like you are), or you are choking the turbine side.
Also, how do you figure 86lb/min, did you base this off of a certain VE? If you assume a 82% VE for a 366CI engine at 7000RPM with 14.7psi ambient you would get 86lb/min. But, with the lower ambientpressure you would get ~90lb/min at the same VE, CI. and RPM.
From my experience when the boost tapers off at higher RPM you are either maxing out the compressor (doesnt sound like you are), or you are choking the turbine side.
10-22-2008, 12:45 PM
#3
9 Second Club
We're probably starting to choke it out. Having issues getting more than 20psi right now. 
The IATs are in line for engine heat soak and the cubes we're pushing.
My Temps for the four 147-148mph passes for Sunday at 19.5-20psi were:
Start End Net
64 135 71 off the trailer with ice
82 149 67 Iced down before run
81 158 77 Sitting in staging lanes
70 131 61 Iced down before run
So your net 68 is in there. You are running a few less cubes, runing in hotter weather, longer staging lines and no ice.
Rick
The IATs are in line for engine heat soak and the cubes we're pushing.
My Temps for the four 147-148mph passes for Sunday at 19.5-20psi were:
Start End Net
64 135 71 off the trailer with ice
82 149 67 Iced down before run
81 158 77 Sitting in staging lanes
70 131 61 Iced down before run
So your net 68 is in there. You are running a few less cubes, runing in hotter weather, longer staging lines and no ice.
Rick
10-22-2008, 01:42 PM
#4
I've been looking over my log files from my last track outing. I noticed an anomoly in the amount of boost i'm running. If I set the boost controller to hold 208 kpa it will hold between 205-209 (16psi) for the entire run. Looking at some video the wastegate opens 50-60' after launch (new converter on order). I tried turning up the boost to 225 kpa (18psi) and all my logs show me reaching 220-225 kpa by 6000 rpms in 1st gear, but by 7000 rpms it's tapering off to 205-209 and then stays there for the rest of the pass. On the one of the crappy videos I have I don't think the WG is even opening on the 225kpa setting. I'm waiting for some higher quality videos to make a final call on it though. My IAT's also went up about 15-20 degrees by the end of the pass with the higher boost to the 165 range (start IAT of 97) which seems like a big jump for a 2psi increase. If I turn it up over 16psi now I can see a spike in 1st gear or 2nd gear on the initial hit, but the boost drops 1-2 psi by the end of the gear. It will hold steady at 16psi and below.
In hotter weather I had been able to get 20psi out of the turbo and hold it the entire pass (with no MPH gain). The only real change to the car was eliminating the over axle piece and going straight through under the axle which eliminated about 300 degrees worth of bends and probably 2 feet of piping in a very short distance.
I know that by being rear mounted i'm losing some of the total output of the turbo, but how much output am I losing due to the thinner air? Am I reaching the compressor side choke point (too much compressor rpm)? Air consumption should be around 86lbs/min at 7000 rpms and a 2.05 pressure ratio based off my 135-136 mph trap speed and 3800lb race weight. I haven't pulled my air filter at the track, but I have done it on the dyno before and it showed a zero HP gain so I don't think it's a major restriction. I have a 4" mandrel bend feeding the turbo to a smooth 4"-5" transition.
In hotter weather I had been able to get 20psi out of the turbo and hold it the entire pass (with no MPH gain). The only real change to the car was eliminating the over axle piece and going straight through under the axle which eliminated about 300 degrees worth of bends and probably 2 feet of piping in a very short distance.
I know that by being rear mounted i'm losing some of the total output of the turbo, but how much output am I losing due to the thinner air? Am I reaching the compressor side choke point (too much compressor rpm)? Air consumption should be around 86lbs/min at 7000 rpms and a 2.05 pressure ratio based off my 135-136 mph trap speed and 3800lb race weight. I haven't pulled my air filter at the track, but I have done it on the dyno before and it showed a zero HP gain so I don't think it's a major restriction. I have a 4" mandrel bend feeding the turbo to a smooth 4"-5" transition.
10-22-2008, 01:51 PM
#5
Well, first your pressure ratio would be 2.1 for 16 psi, assuming that your ambient pressure is 14.7psi. But, because you are running in Vegas at altitude (2000ft elveation ambient ~13.66psi) your ambient pressure will be less so your pressure ratio will be higher, actually 2.18.
Also, how do you figure 86lb/min, did you base this off of a certain VE? If you assume a 82% VE for a 366CI engine at 7000RPM with 14.7psi ambient you would get 86lb/min. But, with the lower ambientpressure you would get ~90lb/min at the same VE, CI. and RPM.
From my experience when the boost tapers off at higher RPM you are either maxing out the compressor (doesnt sound like you are), or you are choking the turbine side.
Also, how do you figure 86lb/min, did you base this off of a certain VE? If you assume a 82% VE for a 366CI engine at 7000RPM with 14.7psi ambient you would get 86lb/min. But, with the lower ambientpressure you would get ~90lb/min at the same VE, CI. and RPM.
From my experience when the boost tapers off at higher RPM you are either maxing out the compressor (doesnt sound like you are), or you are choking the turbine side.
http://www.forcedinductions.com/consumption370.htm
I just estimated the last 500 rpm based on the trend.
The 86lb/s min is a guestimate based off of forcedinductions consumption table and the fact my car is trapping mid 135-136 at 3800lbs which is 750 average rwhp which puts me around 900 hp at the crank (th400 + 9" rear). There is quite a bit of fudging and some assumption in the figures but I should be in the ballpark number wise. Do you think it's plausible to lose 100-150 hp through the driveline at this power level? I've always figured drive train loss % decreases as HP increases and never believed in the who 15% manual trans 20-25% auto trans numbers that get tossed around a lot.
I haven't checked my back pressure on the ST80 yet so that's next on my list of things to check. Wouldn't surprise me if it's 3:1 since I'm only on a 1.00 a/r with the 83mm turbine. Could be related to my small IC piping too. My car does seem to be holding it's own pretty well considering it's huge disadvantages.
I'm hoping with my new converter I can 60' harder and get into the power sooner which should pick up 1-2mph in the 1/8 and .1-.2 in ET since my 330' time will be much better. I feel I should be trapping in the 136-138 range in the quarter on 16psi if I get the launch sorted out. Every time I get a better launch my MPH goes up quite a bit. A 1.75 sixty will get me 134 traps while a 1.60-1.65 sixty will get me 136 traps.
Last edited by Zombie; 10-22-2008 at 01:58 PM.
10-22-2008, 02:42 PM
#6
At 750whp with that turbine wheel and a 1.1 a/r we were above 2:1 already with a 6l (16psi in the intake and almost 40 in the exhaust). That was with a 6 speed manual car so about 830-50fwhp.
Above that power level on a 5l or bigger engine I would recommend using the 87mm turbine wheel with a bigger a/r.
Although that is going to compound your 60ft problem, its tuff with a rear mount.
Above that power level on a 5l or bigger engine I would recommend using the 87mm turbine wheel with a bigger a/r.
Although that is going to compound your 60ft problem, its tuff with a rear mount.
10-22-2008, 02:50 PM
#7
At 750whp with that turbine wheel and a 1.1 a/r we were above 2:1 already with a 6l (16psi in the intake and almost 40 in the exhaust). That was with a 6 speed manual car so about 830-50fwhp.
Above that power level on a 5l or bigger engine I would recommend using the 87mm turbine wheel with a bigger a/r.
Although that is going to compound your 60ft problem, its tuff with a rear mount.
Above that power level on a 5l or bigger engine I would recommend using the 87mm turbine wheel with a bigger a/r.
Although that is going to compound your 60ft problem, its tuff with a rear mount.
That is part of the reason why he hasn't swapped to the larger A/R and turbine wheel. Rear mounts and autos are tough to get just right. Swapping just the wheel and A/R would gain big mpg, but ET would suffer even worse. Hopefully that new convertor will address the leaving issue then we can step it up on the power.
Trending Topics
10-22-2008, 03:52 PM
#8
At 750whp with that turbine wheel and a 1.1 a/r we were above 2:1 already with a 6l (16psi in the intake and almost 40 in the exhaust). That was with a 6 speed manual car so about 830-50fwhp.
Above that power level on a 5l or bigger engine I would recommend using the 87mm turbine wheel with a bigger a/r.
Although that is going to compound your 60ft problem, its tuff with a rear mount.
Above that power level on a 5l or bigger engine I would recommend using the 87mm turbine wheel with a bigger a/r.
Although that is going to compound your 60ft problem, its tuff with a rear mount.
That is part of the reason why he hasn't swapped to the larger A/R and turbine wheel. Rear mounts and autos are tough to get just right. Swapping just the wheel and A/R would gain big mpg, but ET would suffer even worse. Hopefully that new convertor will address the leaving issue then we can step it up on the power.
I'm going to swap to the new converter, see how it runs, then change to a 1.25 a/r housing and see if that makes a difference. After that we are going to play with the turbo some by changing the wheels/covers, but stick with the 80mm size. Jose thinks that with a 1.25 and 87mm turbine wheel I'll only lose 300-400 rpms in spool from what I have now which I probably won't notice with the new converter if everything goes as planned. I think I'm going to have my manifolds ceramic coated to help keep in even more heat.
I've been maxing out every turbo setup I've had on the car so far.
67mm .81 a/r went 125mph on 17psi shifting at 6500 rpms (6spd trans)
76mm .70 a/r went 127mph on 17psi shifting at 5900 rpms
76mm .81 a/r went 133mph on 19psi shifting at 6100 rpms
76mm .96 a/r went ???mph on 19psi shifting at 6800 rpms (turbo died before i made it to the track)
80mm 1.0 a/r goes 136mph on 16psi
My setup keeps getting better as 1320 and I keep tweaking it. MPH is going up and boost is coming down so my effeciency is going up.
These changes are going to take a few months since I'm only making small changes per track trip and there are only two more track days left for me this year. I'll keep posting up my results as I get them though.
Last edited by Zombie; 10-22-2008 at 04:03 PM.
10-22-2008, 04:34 PM
#9
TECH Fanatic
iTrader: (7)
Join Date: Mar 2004
Location: NC
Posts: 1,028
Likes: 0
Received 0 Likes
on
0 Posts
I called Jose and had a discussion with him about the issue, turbine choke lol
I'm going to swap to the new converter, see how it runs, then change to a 1.25 a/r housing and see if that makes a difference. After that we are going to play with the turbo some by changing the wheels/covers, but stick with the 80mm size. Jose thinks that with a 1.25 and 87mm turbine wheel I'll only lose 300-400 rpms in spool from what I have now which I probably won't notice with the new converter if everything goes as planned. I think I'm going to have my manifolds ceramic coated to help keep in even more heat.
I've been maxing out every turbo setup I've had on the car so far.
67mm .81 a/r went 125mph on 17psi shifting at 6500 rpms (6spd trans)
76mm .70 a/r went 127mph on 17psi shifting at 5900 rpms
76mm .81 a/r went 133mph on 19psi shifting at 6100 rpms
76mm .96 a/r went ???mph on 19psi shifting at 6800 rpms (turbo died before i made it to the track)
80mm 1.0 a/r goes 136mph on 16psi
My setup keeps getting better as 1320 and I keep tweaking it. MPH is going up and boost is coming down so my effeciency is going up.
These changes are going to take a few months since I'm only making small changes per track trip and there are only two more track days left for me this year. I'll keep posting up my results as I get them though.
I'm going to swap to the new converter, see how it runs, then change to a 1.25 a/r housing and see if that makes a difference. After that we are going to play with the turbo some by changing the wheels/covers, but stick with the 80mm size. Jose thinks that with a 1.25 and 87mm turbine wheel I'll only lose 300-400 rpms in spool from what I have now which I probably won't notice with the new converter if everything goes as planned. I think I'm going to have my manifolds ceramic coated to help keep in even more heat.
I've been maxing out every turbo setup I've had on the car so far.
67mm .81 a/r went 125mph on 17psi shifting at 6500 rpms (6spd trans)
76mm .70 a/r went 127mph on 17psi shifting at 5900 rpms
76mm .81 a/r went 133mph on 19psi shifting at 6100 rpms
76mm .96 a/r went ???mph on 19psi shifting at 6800 rpms (turbo died before i made it to the track)
80mm 1.0 a/r goes 136mph on 16psi
My setup keeps getting better as 1320 and I keep tweaking it. MPH is going up and boost is coming down so my effeciency is going up.
These changes are going to take a few months since I'm only making small changes per track trip and there are only two more track days left for me this year. I'll keep posting up my results as I get them though.
I think you should just send the turbo to me and let me try it out... haha What caused your T-76 to go out? IM going to get a BB t-78. Was your t-76 ballbearing and did it spool quick?
Justin
10-22-2008, 06:56 PM
#11
I'm kinda surprised no one has really tried to duplicate my setup execpt 1320 (he's done 2 other cars like mine and both are fast and still together). My whole setup could be duplicated for well under 20k including the car since I've posted all the info.