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Running Twins Do They Need To Be Identical?

akaaa7

By akaaa7,
in Engines & Forced Induction

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akaaa7 Enthusiast

akaaa7

Posted
Posted

hey people i have a 'unopened hks 2530' that runs really well and another thats in need of a rebuild. my question is that if i rebuild one with garrett internals will this be a problem when running twins as they will not be the same? any thoughts appreciated cheers cam

Don Dada Mentor

Don Dada

Posted
Posted

If one needs a rebuild its more than likely the other would need to in the near future as well, as they would of been working side by side their entire life

Do both so they would have the same internals and save yourself some headache down the road

The Dan Grand Master

The Dan

Posted
Posted

Can anyone explain to me why they need to be the same?

Two turbos join into one pipe. What difference does it make if one performs less? As long as the turbine is the same size, due to the fact they are both made by Garret and are exactly the same, it's not going to be any different if one is 50 years old and the other is 5 minutes old

sucram Rising Star

sucram

Posted
Posted

cut your losses, sell the remaining good turbo and buy a set of -5's

If your going to use the HKS housing, the comp needs to be welded and remachined due to the smaller inducer on -5's.

The only way to get around this is if you use -10's but you will still need to machine the comp cover to suit the larger wheel.

Then you have a problem with laggy turbos.

By the time you spend $900 on each CHRA, plus machining/welding you may as well buy a new set of -5's for $2200

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Can anyone explain to me why they need to be the same?

Two turbos join into one pipe. What difference does it make if one performs less? As long as the turbine is the same size, due to the fact they are both made by Garret and are exactly the same, it's not going to be any different if one is 50 years old and the other is 5 minutes old

Age.

Put one turbo that has 80,000kms on it against one that had zero, there is a massive reliabilty issue here.

At least with a set of 2nd hand turbos they will *most likely* have the same KM's.

Was recently talking to someone that each year throws out/replaces their set of -5s (on a race car). Each time they pickup 15-20rwkw each time (on around 28-30psi IIRC). I found this to be quite interesting.

Obviously race car season is a bit different but use 80,000kms @ 20psi, however it is still wear and tear which is highlighting this problem.

iplen Mentor

iplen

Posted
Posted

Fix 1, spend all that time and effort putting it back together, then have the other turbo let go, and pull it all apart again?? You can keep that job... Seriously just fix them both..

The Dan Grand Master

The Dan

Posted
Posted

What you are all saying is true, and while I would always get both done together, age is not really a good answer as to why you must do it.

Two turbos of equivalent specifications (wheel sizes etc) no matter how old one is and how degraded one is, it will make no difference to the car actually running. It will do no damage because of some invisible imbalance in flow between the two turbos. Both will push air. Whether both push the same amount does not matter one single bit.

I am only looking at this from a technical perspective. It doesn't mean I would do just one or whatever, just trying to find out why people think there has to be equal flow from both turbos for it to be 'safe' or correct

paulr33 Grand Master

paulr33

Posted
Posted

but as far as common knowledge goes running twins it's a good idea to have them of equal spec or standard

ie dual cpu

make sure you buy both cpu's at the same time, so hopefully form the same build batch and spec

hard disks in a raid setup

maek sure you buy all the drives at once and hopefully from the same vendor, batch build and firmware on the drives etc

ram banks in pairs

buy them at the same time so you reduce risk of minor chip differences

doesnt guarantee, but certainly reduces the risk of differences

akaaa7 Enthusiast

akaaa7

Posted
  • Author
Posted

cheers for all the replies guys, rang gcg for a rebuild price and they were pretty shit on the phone to be honest, talking to some guy that had no idea and goes starting from 850 but i can see that price getting blown out the window from the research ive done and peoples answers. im goin to save the pennys for new turbos... on the topic of running identical twins though what would happen if u ran two completely different size turbos such as -5 and say a gt35r? not that i would or want to but would this damage ur engine if u had both join up into the one intake? im guessing the back pressure of the smllaller turbo could cause a difference in torque to one half of the crank to the other ??? mmm just thoughts

The Dan Grand Master

The Dan

Posted
Posted

cheers for all the replies guys, rang gcg for a rebuild price and they were pretty shit on the phone to be honest, talking to some guy that had no idea and goes starting from 850 but i can see that price getting blown out the window from the research ive done and peoples answers. im goin to save the pennys for new turbos... on the topic of running identical twins though what would happen if u ran two completely different size turbos such as -5 and say a gt35r? not that i would or want to but would this damage ur engine if u had both join up into the one intake? im guessing the back pressure of the smllaller turbo could cause a difference in torque to one half of the crank to the other ??? mmm just thoughts

Yeah the restriction in one side would cause a variation in flow on the exhaust by too much. It would throw out the engine's efficiency by a mile and cause all sort of problems I care not to think about at 11pm

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