compound boost. turbo on ctsv, gt500, ford gt, terminator... keeping the blower
11-22-2013, 08:23 AM
#41
Anyone care to talk about appropriate turbo size? Let me lay out the details.
Mild cam lsa, stock blower, wanting 1000rwhp. I estimate it will take around 25psi to get there and 120lbs of air. Split that and you are looking at 60lbs of air each. Looking at the chart above 9psi blower and 10psi turbo should get 25psi total. I need a pair of turbos that are happy at 60lbs each at 10psi(1.7p/r)
A pair of 76's would be on the map. 88's would be in the sweet spot.
Options are a pair or 67's with An e cover(3" inlet, 2" outlet) mounted where the cats go, or a pair of 76's or 88's at the back of the car. There are no maps for the new stuff but if you look at a map for an old 66 that airflow and p/r are off the map.
A pair of 88's might sound nuts but I believe a 6.2l motor at 1.6bar would act like a 10L engine. Would a 10L engine spool a pair of 88's. Sure but it might be a little laggy. I could see it jump to 9psi and then take a minute for the boost from the turbo to kick in.
Mild cam lsa, stock blower, wanting 1000rwhp. I estimate it will take around 25psi to get there and 120lbs of air. Split that and you are looking at 60lbs of air each. Looking at the chart above 9psi blower and 10psi turbo should get 25psi total. I need a pair of turbos that are happy at 60lbs each at 10psi(1.7p/r)
A pair of 76's would be on the map. 88's would be in the sweet spot.
Options are a pair or 67's with An e cover(3" inlet, 2" outlet) mounted where the cats go, or a pair of 76's or 88's at the back of the car. There are no maps for the new stuff but if you look at a map for an old 66 that airflow and p/r are off the map.
A pair of 88's might sound nuts but I believe a 6.2l motor at 1.6bar would act like a 10L engine. Would a 10L engine spool a pair of 88's. Sure but it might be a little laggy. I could see it jump to 9psi and then take a minute for the boost from the turbo to kick in.
Last edited by parish8; 11-22-2013 at 08:33 AM.
11-22-2013, 08:43 AM
#42
Are you still talking about using a pair of turbos to feed a blower? If so then the mass flow rate of the turbos will determine the power, and the boost pressure is really irrelavent. You just want to make sure the turbos are happy at whatever boost they flow enough air. Rough rule of thumb is 10lb/min of air will make 100hp, so for 1000hp you want 100lb/min of air total, at whatever the pressure the turbo is happy. Your twin 76s or single 88 would be a good choice, and like you said the 67s are too small.
Twin 88s are enough turbo for 2000hp, and would not be happy at all on a 1000hp build. Not only would it be laggy, but they wouldnt be accelerated fast enough to get into their ideal part of the compressor map, they would probably just scoot across the bottom.
Twin 88s are enough turbo for 2000hp, and would not be happy at all on a 1000hp build. Not only would it be laggy, but they wouldnt be accelerated fast enough to get into their ideal part of the compressor map, they would probably just scoot across the bottom.
11-22-2013, 09:20 AM
#44
This is a very very good read, I especially enjoyed the part about cylinder clearing by twincharging. http://www.eng-tips.com/viewthread.cfm?qid=174690
11-22-2013, 10:33 AM
#46
This is a very very good read, I especially enjoyed the part about cylinder clearing by twincharging. http://www.eng-tips.com/viewthread.cfm?qid=174690
Twincharging is very benign. Combustion stability is easy to maintain up to very high boost pressures, because of the excellent positive scavenging possible during valve overlap. Fresh cool clean charge every cycle, with all those nasty hot exhaust residuals blown right out through the turbines.
11-22-2013, 10:48 AM
#47
Heck I would compromise and do a pair of 80s with big turbines (s480/96). With a blower they are not going to be that laggy. Get that backpressure ratio down to 1:1 and it will behave like a HUGE n/a engine...lots of fun and gobs of power.
11-22-2013, 01:45 PM
#49
You have to look at the compressor map to see the issue. I think it will take 25psi total to make 1000rwhp. Guessing 1200fwhp is 1000rwhp. 1200fwhp is around 60lbs of air each turbo. To get to 25psi total the turbos will need to be at 10psi or 1.7p/r.
Find a map that has good eff at 60lbs of air at 1.7p/r.
The 88 is right in the sweet spot of 80%, the t76 is closer to 70%, a 61 is completely off the map(lots of heat). This is a lot of my point of making this thread. I believe most people that try this are using too small of a turbo. A pair of 61's would be ideal if it were turbo only but compounded they can not flow that much air at that low of a pressure.
My question is what would it drive like with a pair of 88's? You would have all of the ~ 500rwhp the stock motor and blower put out but how long of a delay before the boost from the turbos ramps in?
I once had a pt88 on a 4.8. I need to see if I have any old logs from that. I think it would be very similar.
Find a map that has good eff at 60lbs of air at 1.7p/r.
The 88 is right in the sweet spot of 80%, the t76 is closer to 70%, a 61 is completely off the map(lots of heat). This is a lot of my point of making this thread. I believe most people that try this are using too small of a turbo. A pair of 61's would be ideal if it were turbo only but compounded they can not flow that much air at that low of a pressure.
My question is what would it drive like with a pair of 88's? You would have all of the ~ 500rwhp the stock motor and blower put out but how long of a delay before the boost from the turbos ramps in?
I once had a pt88 on a 4.8. I need to see if I have any old logs from that. I think it would be very similar.
11-22-2013, 01:55 PM
#51
thanks for that link. very informative. I guess my thoughts about the high overlap theory of "clearing out the room" was close. the cam I plan on using has a alot of overlap,more than what is consudered correct for forced induction. also using lsa heads which are large ports that move alot of air w the large runners. if anytging, I think the exhaust ports could use some improvement from stock, traditionally rectangke port heads use significantly more duration on the exhaust side for gm and aftermarket cams.
This is a very very good read, I especially enjoyed the part about cylinder clearing by twincharging. http://www.eng-tips.com/viewthread.cfm?qid=174690
11-22-2013, 01:57 PM
#52
You have to look at the compressor map to see the issue. I think it will take 25psi total to make 1000rwhp. Guessing 1200fwhp is 1000rwhp. 1200fwhp is around 60lbs of air each turbo. To get to 25psi total the turbos will need to be at 10psi or 1.7p/r.
Find a map that has good eff at 60lbs of air at 1.7p/r.
The 88 is right in the sweet spot of 80%, the t76 is closer to 70%, a 61 is completely off the map(lots of heat). This is a lot of my point of making this thread. I believe most people that try this are using too small of a turbo. A pair of 61's would be ideal if it were turbo only but compounded they can not flow that much air at that low of a pressure.
My question is what would it drive like with a pair of 88's? You would have all of the ~ 500rwhp the stock motor and blower put out but how long of a delay before the boost from the turbos ramps in?
I once had a pt88 on a 4.8. I need to see if I have any old logs from that. I think it would be very similar.
Find a map that has good eff at 60lbs of air at 1.7p/r.
The 88 is right in the sweet spot of 80%, the t76 is closer to 70%, a 61 is completely off the map(lots of heat). This is a lot of my point of making this thread. I believe most people that try this are using too small of a turbo. A pair of 61's would be ideal if it were turbo only but compounded they can not flow that much air at that low of a pressure.
My question is what would it drive like with a pair of 88's? You would have all of the ~ 500rwhp the stock motor and blower put out but how long of a delay before the boost from the turbos ramps in?
I once had a pt88 on a 4.8. I need to see if I have any old logs from that. I think it would be very similar.
I would find out how many lbs per min your blower moves... Then add 60-70% To that to size a single turbo to fit your compound needs. If the blower moves 60lbs per minute I'd look for a turbo that flows 96ish lbs per minute and go from there. S475 with the largest t6 housing and wheel would work great if the above was correct IMO.
11-22-2013, 02:04 PM
#53
We know how much airflow I need to make 1000rwhp. We have a good idea how much boost that would be on a lsa. We know the boost of the turbo and of the blower.
My figures are fairly accurate. Find a turbo that flows 120 lbs of air at a 1.7p/r. Or find a pair that flow 60lbs each at a 1.7p/r.
Of the maps I can find a pair of t88's would be ideal IF I was looking for max eff(least heat) and did not care about lag.
Look at it another way. An lsa at 1.6 bar is the equivalent of a 10L engine. What is the ideal turbo for a 10L engine that you want to make 1200fwhp? It is going to need to flow a ton of air at a modest boost level.
My figures are fairly accurate. Find a turbo that flows 120 lbs of air at a 1.7p/r. Or find a pair that flow 60lbs each at a 1.7p/r.
Of the maps I can find a pair of t88's would be ideal IF I was looking for max eff(least heat) and did not care about lag.
Look at it another way. An lsa at 1.6 bar is the equivalent of a 10L engine. What is the ideal turbo for a 10L engine that you want to make 1200fwhp? It is going to need to flow a ton of air at a modest boost level.
Last edited by parish8; 11-22-2013 at 02:11 PM.
11-22-2013, 02:22 PM
#54
We know how much airflow I need to make 1000rwhp. We have a good idea how much boost that would be on a lsa. We know the boost of the turbo and of the blower.
My figures are fairly accurate. Find a turbo that flows 120 lbs of air at a 1.7p/r. Or find a pair that flow 60lbs each at a 1.7p/r.
Of the maps I can find a pair of t88's would be ideal IF I was looking for max eff(least heat) and did not care about lag.
Look at it another way. An lsa at 1.6 bar is the equivalent of a 10L engine. What is the ideal turbo for a 10L engine that you want to make 1200fwhp? It is going to need to flow a ton of air at a modest boost level.
My figures are fairly accurate. Find a turbo that flows 120 lbs of air at a 1.7p/r. Or find a pair that flow 60lbs each at a 1.7p/r.
Of the maps I can find a pair of t88's would be ideal IF I was looking for max eff(least heat) and did not care about lag.
Look at it another way. An lsa at 1.6 bar is the equivalent of a 10L engine. What is the ideal turbo for a 10L engine that you want to make 1200fwhp? It is going to need to flow a ton of air at a modest boost level.
You'll need roughly 100lbs/min to make 1000whp.
1.) You said your goal was 1000hp. Why do you need 2 turbos capable of flowing enough air for 2400hp alone? Couple that with the blower and you might even double that number?
2.) Why do you think the secondary charger(s) need to make 120lb at 1.7?
3.) Look at hellions websight. On a 2003 cobra they use the OEM blower and 2 61mm turbos and make over 1000whp.
11-22-2013, 02:33 PM
#57
1. My experience is the lbs of air is closer to fwhp than rwhp. For example I maxed out a pt88 at 1024rwhp and it is rated at 1250lbs. This experience may not match what others have seen and I would be happy to adjust my numbers accordingly but that will only make the problem of finding a matching map worse.
2. It will only take 10psi from the turbo boost to equal 25psi at the valve. 10psi is 1.7bar. I explained the 120lb of air above but we can use 100lbs total.
3. If my hp goal required me to run 40psi then a smaller turbo would work. I do not expect to have to go over 25psi so that changes the maps we are looking at. I also believe there set up would make more power with less boost(more eff) if it had larger turbos.
I attached a map for a s475. Look where 1.7bar and 100lb/120lbs lands.
2. It will only take 10psi from the turbo boost to equal 25psi at the valve. 10psi is 1.7bar. I explained the 120lb of air above but we can use 100lbs total.
3. If my hp goal required me to run 40psi then a smaller turbo would work. I do not expect to have to go over 25psi so that changes the maps we are looking at. I also believe there set up would make more power with less boost(more eff) if it had larger turbos.
I attached a map for a s475. Look where 1.7bar and 100lb/120lbs lands.
11-22-2013, 02:51 PM
#58
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Excellent reading on this subject in this thread. There are a handful of 3800 twincharged GTPs around the country that have done this with excellent results. I thought about using a compound setup with a quickspool valve on a T3 turbo and a ball bearing T4 staged in series, but The most difficult problem is complexity, weight, and tuning. Since the torque factor is multiplied greatly I can't really see many gas V8s doing this. The quick spool valve has made it much easier to get good (useable) power down low so Compounding is not feasible. Totally badass however...!
11-22-2013, 03:17 PM
#60
1. My experience is the lbs of air is closer to fwhp than rwhp. For example I maxed out a pt88 at 1024rwhp and it is rated at 1250lbs. This experience may not match what others have seen and I would be happy to adjust my numbers accordingly but that will only make the problem of finding a matching map worse.
2. It will only take 10psi from the turbo boost to equal 25psi at the valve. 10psi is 1.7bar. I explained the 120lb of air above but we can use 100lbs total.
3. If my hp goal required me to run 40psi then a smaller turbo would work. I do not expect to have to go over 25psi so that changes the maps we are looking at. I also believe there set up would make more power with less boost(more eff) if it had larger turbos.
I attached a map for a s475. Look where 1.7bar and 100lb/120lbs lands.
2. It will only take 10psi from the turbo boost to equal 25psi at the valve. 10psi is 1.7bar. I explained the 120lb of air above but we can use 100lbs total.
3. If my hp goal required me to run 40psi then a smaller turbo would work. I do not expect to have to go over 25psi so that changes the maps we are looking at. I also believe there set up would make more power with less boost(more eff) if it had larger turbos.
I attached a map for a s475. Look where 1.7bar and 100lb/120lbs lands.
A stock gt500 long block with the proper fuel will make over 1000whp easily with twin 61mm turbos through the OEM charger at 17lbs of manifold pressure.