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T3 Turbo Sizing


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Having lived w/ turbo cars since the mid 80's I would suggest that any car that will be used as a daily driver have a water cooler center section.


When by '83ZXT's turbo finally shot craps I used a Turbonetics water cooler T3 and it currently has more miles than the original turbo and is going strong.



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You are absolutely right, just re-did the math with the SX252e and I'd need 13.8psi to get to 350 on the crank @6500 -- see map attached.

Do you think a WG spacer will do in this case? 


I am still unsure if I should:

  • run the flattops with a stock gasket
  • flattops with a thicker (1 or 2mm) gasket
  • get dished pistons
  • go forged


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You have to bleed off enough exhaust that the impeller speed does not ramp up and build too much boost. First hand I know that a 256sx (which is even less efficient then the sx-e), has boost creep even with a 40mm waste gate on full open when it is in a mediocre priority path, a wastegate spacer has bad priority and if memory serves can only accommodate a 38mm waste gate. Only downfall is that you won't be able to make less power if you max out your waste gate. 


Research, look up other people's builds, see what makes sense to you and come back with a plan. I really want to avoid spoon feeding too much, we have a massive resource here would be good to take advantage of it.


I will say, with a lower octane of available gas, high compression, non cross flow design you kind of have a perfect storm for knocking. You are going to have to address that. Up to you what path you choose and how much you want to spend. Forged internals at that power level might be superfluous if you have a safe tune. Keep in mind if you up the power you are going to have to think of the parts down stream, clutch, trans, half shafts, diff, etc etc.

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Thank you! I got a 50mm wastegate and will add the piping directly to the manifold.


As for the pistons, I will wait and see how the current pistons look like. I am still not sure if forged or just dished.

I will go for a safe tune, monitoring as many things as possible.  :)


Thank you again for all the info -- helped me a ton!

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My 2 cents…. 

When selecting a turbo, as mentioned above definitely get one with a water cooled center section. If you can afford it, also get one that has ball bearings rather than a sleeve bearing. They last longer and you typically get the latest technology sinc turbo manufactures are putting most of their r&d into ball bearing turbo’s. 
If you already know this then please disregard my comments. Making horsepower with a turbo is not a function of psi. Psi is essentially a measure of resistance. It’s all about volume of air flow. Not pressure. For example, turbo A might flow lets say 35 lb/min at 17 psi while turbo B might flow 50 lb/min at the same psi and at the same efficiency island. The difference in these turbo examples are typically their size and technology. Flow maps will show you the cfm at various psi for various efficiency levels. Try to match your turbo selection to the cfm (at a streetable psi) required to make your hp target. Then there’s lag to consider. As has been stated above the turbine housing size will affect lag. The smaller the a/r the quicker the spool up but at the same time a small a/r can restrict high rpm performance because of exhaust pressure. I’ve found that a small a/r turbine housing is difficult to drive because it has so much bottom end at the expense of the top end. It’s a matter of preference. I went from a T3 .63 a/r to a T4 .82 a/r. I didn’t notice much of a change in the bottom end but I did notice quite an improvement in the midrange and top end. Again it’s a matter of preference and driving style.
Also take into consideration the cfm flow of your head/cam. The cfm of your head and cam (that’s a whole other discussion) will give you a ball park of the max cfm your engine can move which in turn gives you an idea of the turbo cfm your engine can handle. Too big of a turbo and you’re adding more flow than your engine can handle thus creating flow resistance (unequal pressure before and after the turbine housing) while typically introducing increased turbo lag. Too little and you’re leaving hp on the table. Simply, it’s about the amount of cfm required to meet your hp goal, and whether or not your head/cam can flow those cfm numbers. Then select a turbo that makes that amount of cfm, at a streetable psi, at the sweet spot or close to the sweet spot of the turbo’s flow map. And lastly don’t forget to port your turbo exhaust manifold especially where runners 1-2-3-4 come together just before the exhaust flange. 
The trick is to get everything to work together in balance. Good luck.
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^Interesting, I imagine in a L28ET? How much did you see your power band move? HP gains? I just ordered my turbo and went from a 0.83 to a 0.68 in T4. The tech and I were very happy when we found that choice. I can see your point if the turbo spools too much at the bottom end it will hit a bit hard which makes it harder to ease into. Overall it didn't seem like too much of a difference a couple hundred RPM in spool location and the potential for a bit of horsepower (as far as I know), but it is true it depends on your end goal if you want more power go bigger A/R and have a smaller power band, or go with a smaller A/R and have a broader power band but maybe loose some power at the top end. An interesting benefit if running a small A/R I was told was that due to the increased exhaust pressure a wastegate becomes more efficient for a given size, granted with a bigger A/R you would need more exhaust to spool.


Please don't take this as arguing, it would be nice to hear your thoughts on the matter.


Regarding water cooling, I wonder if that is still the case with modern oils and knowledge of just cooling the car off prior to shut off. The point from what I understand was that when shut off the heat would basically bake the oil and cause earlier failure, but as long as you run a cooldown regiment and quality oil I wonder if that is still a big concern. A lot of single turbo supra guys don't run water cooling, but at the same time I wonder how much a car that needs a single turbo gets driven.


Regarding ball bearing, How much longer are we talking about? Usually the ball bearing models run about 4-500 more, at that price you could buy a new center section or several rebuild kits. I personally like BW at the moment as it is the SX line which uses old designs, but still feature extended tips and such, SX-E line which has the new billet wheel and non clipped exhaust wheel along with other upgrades, then the EFR turbos which are just going nuts with integrated compressor valves, exotic material for the wheels, stainless housings etc.

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Personally if you have the funds (and are stuck on T3) I would go Precision PT6062 T3 82 A/R with 3" V-Band discharge. I agree with Tim0, too many people pick too small of a turbo. I run an 80mm T6  1.10 A/R on my 5.3 and its a torque monster and it spools fast. The amall exhaust housings limit power up top due to excessive back pressure.

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^That is way way too big for his goals.


A wastegate spacer  has horrendous priority and most likely isn't going to be able to fit a big enough waste gate bad for big and small turbos

Maybe...BUT power is addictive and I bet he'll soon be wanting more.  I would recommend getting a modern a turbo with room to grow.

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300 hp on a 2400lb Z is awesome. But as Rossman said, power is addictive. 300 hp will only satisfy for a year or so then it feels tame. Next thing you know you want 400+ hp. Ask me how I know! On an L series engine the three main components that people tend to spend more money redoing a second or third time is converting to forged pistons, head/cam, and the heart of the turbo motor...the turbo. If you want 300 hp build for 400. Spend the money once!  

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I guess it depends on what you plan on doing with it, where you are going to drive it, if you want room to grow. I've been reading a lot on the supra forums and over there people go way bigger "just in case" to the point it just seems excessive.


Up here where it is damp most of the time I didn't have traction in 3rd if I romped on the throttle at around 300hp, my friend and I were talking and short of a race track there just isn't too much road where you could take advantage of high hp, but plenty of roads you can take advantage of with good suspension. I guess it depends on your area. I just can't imagine wanting more in such a light car unless drag racing or highway pulls are your cup of tee, but...with that said I'm moving up to about 400hp this time around, I swear for me it was more or less to justify this engine swap as swapping in another engine for the same hp would be a bit silly :P


I guess I'll have to agree, if you have the budget for it, it is nice to build for room to grow within reason. Granted the other crutch is if you have room to grow its like having a pile of cocaine on the table, you might have thought you never would use it, but it is there, the temptation is going to be hard to resist.

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I would suggest that if the car is basically street/highway driven that you size the A/R of the turbine section so that you are not in boost when cruising on the expressway for gas mileage purposes.


Perhaps those with experience can make a suggestion based on the 50 trim compressor section turbo and the GT35...

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  • 4 weeks later...


I am currently converting my Z from carbs to turbo. 
F54, P90 head, flattop pistons, 60mm 240sx tb, 440cc injectors, intercooler, upgraded pump and lines
I want between 300-350hp to the wheels and want the turbo to spool between 2.000-2.500 but also have some top-end power.
I currently have my eye on these Turbonetics options:
T3 w./ 60-1 HiFi, st. bearing, oil cooled, F1-57, and .64 A/R (maybe .48?)
T3 w./ T04E Super 60, st. bearing, oil cooled, F1-54 and .64A/R 
What do you guys think would be my ideal choice? 
Thank you!!!




Want spool and power?  The old thinking of bigger turbo's wont spool fast is gone. You need bigger exhaust flow to make power or your choking the engine. I suggest the below unit. Ceramic ball bearing, it will spin.


Turbonetics T-SERIES

  HP 66 4.0"/2.5"  F1-65 T4 0.81 A/R 4-bolt / 3" V-band
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