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cosmo

T3 Turbo Sizing

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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?)

 

OR

 

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!!!

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Look up a compressor map and find a turbo that has a good efficiency island at a pressure ratio desired at 2, 2.5, and 3k rpm on I am guessing a 2.8L engine for the amount of horsepower you are looking for 35cfm from the sounds of it. There are formulas and calculators.

 

https://turbobygarrett.com/turbobygarrett/plotting_data_on_compressor_map

 

Excellent walk through. 

 

Spool usually means when a turbo is making peak psi. A turbo that makes peak psi at 2.5-3k is going to be a massive restriction on your exhaust at higher rpm, unless you have a massive prioritized waste gate. 

 

If you don't learn to look at compressor maps you are going to be at the mercy of someone's recommendation and their interpretation of spool or the boost threshold. 

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Thanks guys the links helped a lot!!

 

So after doing some math, I got to around 37.95 lb/min for 345hp (should get me in the 300whp ballpark) which then translates to around 18.4psi of boost (calculated with 5.6k RPM) and a pressure ratio of 2.55.

 

After translating that to the compressor maps I saw that the 60-1 is definitely too big for my needs/wants.

 

So my favorite right now: T04E50 Trim, what do you guys think? Also, does anyone know where to get ALL Turbonetics maps for their current lineup? I only found 7 on their website.

 

Vm7MUVT.jpg

Edited by cosmo

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Thanks guys the links helped a lot!!

 

So after doing some math, I got to around 37.95 lb/min for 345hp (should get me in the 300whp ballpark) which then translates to around 18.4psi of boost (calculated with 5.6k RPM) and a pressure ratio of 2.55.

 

It's not a terribly big deal at this point but 18.4psi boost does not result in a PR of 2.55 - more like 2.25.  Typo maybe, or trying to account for losses through the induction system?

Edited by TimZ

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Way to take it in stride man. 

 

That would be a good turbo for your needs from a quick glance. Doesn't look like you would have too much room to grow, but the spool should be happening on the lower side of things which seems to be your bigger priority. 

 

I would recommend a look at the SX-E line from borg warner if you a bit of budget to play with. Their offerings are pretty substantial, a lot more efficiency on tap so you can run that same 50mm inducer wheel to higher boost levels before you start heating up the air.

 

Curious what the desire for the low spool rpm was. 2k rpm is pretty much a touch of the throttle, do you want that instant response like from a bigger engine? If that is the case then this is all wrong as you are looking for a supercharger. 

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I'd definitely be looking at a good set of Forged pistons at anything over 10 lbs of boost. I see you're in California? What are you planning to run for fuel. If 91 pump gas, you're going to have to keep the CR down to around 9.0, unless you run a lot of H20/Meth injection ( Well recommended ) .

 

We have some high CR Turbo cars running locally in the PNW .  Keth L run 10.1+ CR on his stroker L20B ( 2.3 L ) . 16 lbs boost, with big intercooler ,Water/Meth and C16 fuel!! But he pushes 300 RWHP out of that 4 banger all the time.  ( No E85 up here  to speak of ) . Can you get E85 in California? Go for it if you can.

 

A good EFI system will help keep things alive. The AEM Infinity series have gotten a lot of good reviews ( although they do have a recall on now for early models with a weak Internal Power relay ). Audi/VW guys are really liking them. Haltech is also really, really good but $$$. Whatever you decide to use, I would definitely set it up with twin Bosch WB Knock sensors on a Forced Induction motor. Modern EFI systems have all the tuning and Data logging tables to make adjustment of modern WB Knock sensors relatively easy.  

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This fast enough spool for you? AWD Rabbit with 2.0 L VW 16 valve  Turbo engine. GT2871R ( Ball Bearing Turbo )  around 18 lbs boost. Virtually no lag. Josh  Autocrossed this car as well. Would work well on an L24 and give you more than enough power.

 

https://www.youtube.com/watch?v=fiYg9okV-ME

Edited by Chickenman

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Thanks for the input guys!

I wanted a quick spooling turbo but you are right, after going through all the maps 3k sounds pretty 'right' to me.

 

I thought of either getting forged pistons or getting a 2mm metal gasket which would give me a CR of 7.86:1with the flattops.

91 fuel, Megasquirt 3Pro (at least that's the plan)

 

This is the turbo I thought of getting:

cRQcMul.png

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Do you get a discount if you order from turbonetics? Why are all your selections from them?

 

You are paying a lot for an old turbo with old tech.

 

~750

The SX line has extended tips so flows more air while maintaining the same size

https://agpturbo.com/borg-warner-agp-s251sx-turbocharger/

 

~850 with your desired hotside

The SX-E line has so many improvements for that extra 100$ that it would be silly to try and justify not getting it. Still cheaper then the turbonetics turbo.

https://agpturbo.com/borg-warner-s252sx-e-52-61-12709095019/

 

~850 

The GT28 would reach your power goals and spool quite quickly, these are usually used on 2L SR20's though so you would spool quite a bit sooner with a 2.8L, but most likely run out of puff sooner as well.

 

~775 

Precision 5431 with a billet wheel

http://www.treadstoneperformance.com/product.phtml?p=2304

 

The only downfall is that some of these would potentially flow too well and make too much power would require quite the wastegate. I'm guessing you are running a ZXT manifold so no native waste gate could make some of these offerings difficult to control.

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Thanks @seattlejester!!! 

 

After checking these out I have to admit I really like the S252SX !! I thought of getting the GT28 before but after all the research I think it might be a tiny bit too small.

 

I will be running a wastegate (T3-T3 spacer with WG outlet) to get the boost under control.

 

 

Thank you! 

Edited by cosmo

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For a big hotside it won't matter as much as the exhaust will have somewhere to go, but with your desired short spool requirement that means running a fairly small hotside which means that it will cause a back log and restrict the exhaust. That and the fact the T3 foot print is already small means you are going to have some flow restriction as is.

 

20lbs on a flattop seems pretty high off the bat, not sure you can run that with california 91. Where are you getting your numbers? I am pretty sure the borgwarner turbo's don't need to push nearly that much in fact you would be over 400hp at 20lbs if memory serves. The 256sx makes almost 600hp at 20lbs at 7000rpm. Even I think the GT28 would be quite a bit over 300 at 20lbs if it is still efficient.

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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.

 

YMMV...

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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

jdutgnj.jpg

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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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