Twins on 1100 hp Puller

dieselpolaris

dieselpolaris

New member
Our sanctioning body allows us to run an unlimited single or twins but the twins are limited to a 3.0 charger. We are allowed to run bushings though so I was curious as to how big a person should bush down before the turbo is starting to loose efficiency. Only planning on running around 4500 rpms down track. My original plan was using a s468 with 1.0 exhaust housing 83mm turbine and putting an s488 with a billet wheel and race cover and 1.32 exhaust housing under that and bushing that 3.0 inlet. Just wondering if id be better off with like an S480 instead since that would have to be bushed down alot less. Also do you guys think a regular off the shelf s468 will be fine as a secondary in this configuration or does that need a billet wheel as well? Thank you :Cheer:
 
IMO 3" twins are practically a waste of time, especially on a manual trans truck.

You can easily spool a 3" single, and potentially much larger...so why bother? We have a class just like that around here and nobody is running twins. They put the twin provision into the rules so that a set of street twins has a place to hook.
 
dieselpolaris said:
Our sanctioning body allows us to run an unlimited single or twins but the twins are limited to a 3.0 charger. We are allowed to run bushings though so I was curious as to how big a person should bush down before the turbo is starting to loose efficiency. Only planning on running around 4500 rpms down track. My original plan was using a s468 with 1.0 exhaust housing 83mm turbine and putting an s488 with a billet wheel and race cover and 1.32 exhaust housing under that and bushing that 3.0 inlet. Just wondering if id be better off with like an S480 instead since that would have to be bushed down alot less. Also do you guys think a regular off the shelf s468 will be fine as a secondary in this configuration or does that need a billet wheel as well? Thank you :Cheer:
Click to expand...

Unfortunately there are a lot of variables that play into that. I don't think you could collectively say for instance, bushing down 0.5" is the limit on all/most turbos. Your best bet (IMO) would be to talk to the guys that are going to build your turbo(s) and see what they recommend.

I am toying with a similar scenario, but it is what Mat referred to. Unlimited single or 3.0 protrusion on both chargers... I don't really like the latter option.

Edit: I'm shooting for a bit more than 1100 hp though.
 
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nwpadmax said:
IMO 3" twins are practically a waste of time, especially on a manual trans truck.

You can easily spool a 3" single, and potentially much larger...so why bother? We have a class just like that around here and nobody is running twins. They put the twin provision into the rules so that a set of street twins has a place to hook.
Click to expand...

Very good advise!
 
Wouldnt you guys agree that a twin setup should be much more forgiving depending on track conditions and overall more efficient. Intake temps should be lower since the chargers do not have to work as hard to make the same psi of boost. Another thing a person should be able to gear the truck for a higher final ratio and not fall under the charger down the track? Momentum is your friend is my thinking when it comes to pulling. The faster i can go the harder it is to stop. Does this theory make sense?
 
If you were to go with a large set of twins and bush the atmospheric charger then the high pressure charger will create drive pressure problems in the high rpms. Just go with a large single and tune the engine to carry higher rpm down the track. Twins are only for street trucks.
 
dieselpolaris said:
Wouldnt you guys agree that a twin setup should be much more forgiving depending on track conditions and overall more efficient. Intake temps should be lower since the chargers do not have to work as hard to make the same psi of boost. Another thing a person should be able to gear the truck for a higher final ratio and not fall under the charger down the track? Momentum is your friend is my thinking when it comes to pulling. The faster i can go the harder it is to stop. Does this theory make sense?
Click to expand...


It has been said many times that twins of equivalent size will never make the top end power that a same-dimension single would. I have not done it myself personally but the experience is out there.

As far as intake temps, you can run a big single and an air/water intercooler and get the heat out. With twins, it totally depends on how you set them up and how well they work with your tuning, etc. as to how cool the charge air is. People assume that they're more efficient but I've done enough spreadsheet calcs to say that you still need to know what you're doing to get the efficiency of the whole system where it needs to be. It is not a foregone conclusion. You have 2 compressors heating the air, both 75% efficient (on a good day)...think about that for a minute. Intercooling is still a requirement, be it water or a heat exchanger.

Also keep in mind that the all the air in the system comes from the low pressure charger. If that's limited to 3.0, even if bushed, it's still too small to make it worth it IMO. The guy beside you is running a 3.6" single...

I agree on track speed, but I'll also say I've seen a lot of open single trucks fly down the track.

I'm not saying you're wrong per se, but I've yet to see a twinned truck *with those limits* outrun the big singles.
 
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nwpadmax said:
It has been said many times that twins of equivalent size will never make the top end power that a same-dimension single would. I have not done it myself personally but the experience is out there.

As far as intake temps, you can run a big single and an air/water intercooler and get the heat out. With twins, it totally depends on how you set them up and how well they work with your tuning, etc. as to how cool the charge air is. People assume that they're more efficient but I've done enough spreadsheet calcs to say that you still need to know what you're doing to get the efficiency of the whole system where it needs to be. It is not a foregone conclusion. You have 2 compressors heating the air, both 75% efficient (on a good day)...think about that for a minute. Intercooling is still a requirement, be it water or a heat exchanger.

Also keep in mind that the all the air in the system comes from the low pressure charger. If that's limited to 3.0, even if bushed, it's still too small to make it worth it IMO. The guy beside you is running a 3.6" single...

I agree on track speed, but I'll also say I've seen a lot of open single trucks fly down the track.
I'm not saying you're wrong per se, but I've yet to see a twinned truck *with those limits* outrun the big singles.
Click to expand...

turbine configuration is the factor on choking at the end or pulling out strong.....
 
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