Individual turbo upgrade

[smitty]

After days of trawling the threads, it's pretty clear that the stock turbos, although providing good drivability, run out of puff rather early, due to their (lack of) size.

How about leaving one of them at stock size, but replacing the other with a larger turbo? Theoretically, wouldn't this retain a fair amount of low-down punch but also provide more puff at higher RPM?

Is it even possible to run two different turbo sizes?

 

[weeaazz]

this has been covered before but not for a long time,i beleive the end result was a big NO as it is possible as they have it on rx7s and so on but i think the price to do it properly would be far greater than buying some small garrets that would spool up just as early.

it sounds like a great idea,i thought about it too,but apparently there is far too much involved and twin garret gt25s would give more power and a better curve

[EDIT]

actually now that i think about it,i dont even think its possible,because one half your motor would be getting put under so much more strain than the other with a big turbo.the rx7s setup doesnt have a V like our cars. it would be like using half your engine down low and the other half getting raped to redline.

 

[smitty]

Hm ok then. Just out of interest, exactly how are the turbos set up? Does one turbo feed each bank of cylinders?

Edit: Don't the supras run two different size turbos, albeit sequentially?

 

[Gravid]

yes there is a turbo for each bank

 

[dr-25-lt]

dont quote me on it, but im 90% sure it wouldnt work... for example, i know on the B4 liberty they ran a twin turbo, n i think they were inline twin turbo, which is where the theory of low down boost and top end boost applies. but as stated earlier, one side of the motor would run differently to the other as each turbo works on its own side of the V motor.

 

[weeaazz]

yer ours run a bank each.the engine is west-east with a turbo at the front and the rear of the engine,both run simultaneously.
supras are a straight six,which would work differently

i may be wrong though about running a bigger one,but im pretty sure itwas shunned against last time

 

[godzilla]

The plenum is only fed by one pipe, the two turbos meet up at the Y pipe then go through the cooler. So one bank should not be under any more load running a larger turbo.

 

[smitty]

Hmm so it still might be a go then... I know a bloke who runs a performance shop in Cheltenham, might go pick his brains about it. would be rather cool if it would work.

 

[Guest]

well iv been told its got to do with the exhaus end of the turbo coz one wil have more flow then the other dont quote me on it tho

 

[Guest]

It's been done before with other cars. It's not the most desireable option, but if the turbos were of similar size then there's no reason why it shouldn't work alright. See some of the GTO/3000GT websites - they often upgrade the front turbo to one a size up because it's easy. Personally I'd take the time to do it properly and get the turbos that will give the power that you want.

If one is too large then I'd guess you'd have problems like the turbine choking (because essentially it wouldn't have started spooling properly and the other would be forcing air back through it). Both banks of cylinders would recieve the same air through the inlet plenum, then the turbos would start spinning at different rates. One trying to come on boost quickly. Or just upgrade to a single turbo set up! If there's room. You'd only need to buy one turbo, one dump, one set of oil lines, etc - makes a lot of sense if you want to go straight for big power and let's you relocate the turbo to somewhere more convenient!

FYI Other cars use either 3 cylinders driving each turbo, or the I think the supra has the single turbo which then fires up the secondary as well once a certain boost is reached - the rx7 may be similar to that too - or there's the b4 which has a small turbo which then shuts down and swaps over to a larger one.

 

[Dr_Josh001]

The plenum is only fed by one pipe, the two turbos meet up at the Y pipe then go through the cooler. So one bank should not be under any more load running a larger turbo.

Wrong! The exhaust manifolds having different pressure WILL cause a power difference between the two banks especially at high rpm when the smaller turbo is trying to keep up with the pressure of the larger turbo! Don't do it because you'll stuff your engine!
The only way this could work is if the two turbos were fed from the same manifold but this setup is very tricky and is not common hence it would need to be a custom setup. The other reason it's not common is because it is far more effective to run slightly larger turbos (either 2xTD04H or Garret 2xGT2554R) to still get the bottom end drivability and top end power.

 

[Bennoz]

If your wanting more power, there is an array of different things you can do prior to fiddling with turbos. Have you done the exhaust & intake piping yet? Got a piggy back unit to get the optimum tune out of it?

We've managed to get 270kws at the wheels (albeit only 2 wheel drive) out of a 6A13 donk with the factory turbos in my FTO. The key to getting power out of the little fella's was all in the timing & tuning. At high rpm we found the exhaust timing just wasn't letting enough gas out, all the meantime the inlet side of things were fine. A couple of vernier cam gears on the exhaust bank sorted that out. Im getting solid boost till just before 7,000rpm. After that, we plan on using nos to drag them out further to 7,500.

 

[smitty]

I haven't acquired my VR-4 just yet, but when i do finally get it, i'll be getting everything done at once. At the moment, i'm just trying to do my research so i can make a final decision on where exactly i want to go with the car, and how far i can go in that direction with the funds allowed (approx 15k +/- if all goes accordingly).

What was the cost involved in the vernier cam gears? it'd have to be cheaper than fitting two new turbos. And what other bits'n'peices have you fitted/replaced/played-with prior to fitting the cam gears?

 

[khyle]

how much do these slightly larger turbos set you back approx? to buy n fit. im guessing thats the go then, no bigger than the gt25's or?.. n wat other little upgrades can you get without spending an insane amount of dosh??. ive seen pics of the air pods with the cstom setup n stuff, but jus wonderin if they get that much air flow being set back in the engine bay like that?n that they arent sucking in any hot air from the engine..

 

[mustang21]

im not sure why every one wants bigger turbos, ya can tell whos smart here, power is made on timing and fule mix. if ya gona go bigger turbos ya gona wanna run more boost, stock pistons will hold about 10 PSI befor cracking( its difrent for all cars as build quailty is difrent)


bigger turbo means more fule, more boost, and better timing, its a hole new park going there guys,

dose any one know how much power the auto gear box will hold for a start?? same with man??

the car works 2gether you cant just upgrade one part and expect huge power,

 

[godzilla]

im not sure why every one wants bigger turbos, ya can tell whos smart here, power is made on timing and fule mix. if ya gona go bigger turbos ya gona wanna run more boost, stock pistons will hold about 10 PSI befor cracking( its difrent for all cars as build quailty is difrent)
bigger turbo means more fule, r,

For starters its "Fuel"
Also, where did you come up with the pistons cracking at 10psi?
I think you are missing the point here, the reasons why people are looking at upgrading the turbos is because they will only flow enough for maybe 220-240awkw. By this stage you have already purchased a stand alone ecu, so people are across the fuel/ignition.....

 

[bradc]

I've been running around 16/17psi for nearly two years, maybe my pistons haven't been made aware of it?

 

[frozen]

i been running 12psi with no issues personally brad i reckon 16/17 would be so hot and inefficient that youd make similar power at 14 lol (lets not argue though, cause you'd probably end up proving me wrong and its a totally seperate topic hehe, just poking fun)

and yeah, most people have already done all the fuel & ignition side and maxed power that way - hence going bigger turbos and repeating the process with more flow/ higher boost..

 

[Mortz]

I have a feeling Brad may have changed turbos on his worked Legnum as I'm pretty sure he wouldn't be running stock turbos on 16/17psi...

 

[Legume]

Without opting for bigger turbos (and the lack of space for them), having a more effecient inlet track (and intercooler) and exhaust makes it easier for the turbo to do its thing.

Smaller parallel turbos are used on small cars to reduce lag.*both turbos must have similar back pressure so no putting on one big one and one small one
Sequetial turbos are just a mess. To send exhaust through the smaller one, then redirect it to the lager one (and similar for the compressed air) its all a half arsed effort just to try and get a car that you cant feel the turbos working on and feels like a bigger N/A engine instead. But trying to get someone to make such a thing for a decent price would be impossible. You are only going to get as much power as the biggest one will make minus what has been lost through the ineffiency of the plumbing.


The best ultimate option would be as everybody suggested and get the bigger turbos.Another complicated way would be relocating the battery and what else out of the engine bay and go for a single turbo with an adjusting A/R ratio. These direct the exhaust gas to spin the turbine faster, then open up to flow more.

I would think that similar to what Bennoz did, and looking at the cam, would be of great effect for more top end whilst retaining the original set up and spooling time. Also a porting would allow the manifolds to pass a higher CFM.