Turbo Recommendation

[lr172]

A year ago I added a turbo to my 3.2 carrera along with a Megasquirt EFI (still 9.5:1 CR). It runs great, but I don't get full boost (.6 BAR for me) until 4100 RPM. It has an old T3/T04E with a 60 trim compressor and a Stage 3 turbine (.63 A/R). The oil seals have started to leak some, pushing me to finally get something new. I want something that will spool up sooner. I hear of guys getting good boost by 3K and would like to be one of them.

I also have a hard time holding .6 BAR. It gets there, but in most gears will taper off to .5 BAR. I am thinking that my T04E just isn't producing enough flow. I don't think it is doing what it used to for me.

I have done some research and it seems the GT3076R is a good fit. I redline at 6500 and care more about a quick spool than I do losing a bit of the top end, if that matters.

I have done some research here, but I would love to hear what has worked for you guys and what you think may best fit me goals here.

Thanks for any insight you can provide.

Larry

[RarlyL8]

I use and recommend the K27S on turbocharged 3.2L engines. They are designed for our engines requiring quick spool and low boost pressures.

[911st]

There is a new GTX3076R that just came out that could be a very sweet turbo in the right situation. (Larger than a GT30 and smaller than a GT35) It's sweet spot is closer to 1 bar on an easy breathing EFI build.

It is has one of the newest generation of Forged compressor wheels that is lighter and flows more air for its size.

Are you running a Turbonetics 60-1 turbo?

If so it's compressor map looks like a good fit for a low boost build like yours. If the hot side is sized right and you have an ok exhaust system it should be at .6 bar boost by 3k easy. Even without the BB option.

Turbonetics also look's to have the newest tec forged-wheel 60-1 and 62-1 compressor wheels that might be something to look into.

When looking at a compressor map you probably want to look at about the 1.7 to 1.8 line for an EFI .6 bar turbo. The old 60 and 62-1 turbo's were in there sweet spots in that range.

Most the GT's and other aftermarket turbo's are in the middle of there peak efficiency island at about 1 bar or higher and just do not look on the surface like a very good fit on a low boost build.

You might check with Protomotive and see what they recommend these days for low boost. They used to be the king in that area.

Not an expert, just my two cents.

[911st]

PS,

Here is the GTX3076R and 60-1 compressor maps for reference.

The GT is happiest at about 1 bar and at about 375chp. The 60-1 at about .6 bar and 350chp.

For a street car you kind of want your best turbo efficiency at about your peak torque point. Is so that should make the 60-1 in the range of a good 400chp low boost turbo.

Add about 10% for the Turbonetics 62-1. If you have there hi-flow small frame option take about 10% off each.

Again, not an expert and there may be better options from others.

[DonE]

Since you are EFI and I assume you can control timing, a ball bearing turbo is the only way to go. The size of the turbo is now the question. What size is your turbo flange? I don't know MS, but if you can adjust fuel enrichment and timing, you should be able to light the turbo much quicker and a BB turbo will be a big improvement.

[lr172]

911st,

Thanks for posting the ideas and the content. I took a look at several maps and my T04E is WAY off. No wonder the MAT is getting so high. The 60-1 is too close to the surge line. Surprisingly the 3076 or 3582 seem about the best compromise for my pressure ratio and air flow. I'll do some more digging.

Don e,

Yes, I have full control over the timing and fuel levels. How do I go about getting a quicker spool up. I was not aware that I could impact this through tuning. I would love to learn more if you don't mind. I am using the stock 930 J pipe with a T3 flange. My exhaust is also 2.5" currently, but I plan to upgrade this to 3" when I replace the turbo.

Larry

[911st]

Larry,

What HP range are you looking at?

My guess is about 375chp/ 325whp.

I probably still have a lot to learn about reading turbo maps but it looks like both turbos have almost the same surge limit in the boost range you might operate in.

Would think .6 bar on a 3.2 would be about 360 ft lbs peak TQ at about 5200rpm. That should be about 360chp at TQ peak or about 36 lbs/min air flow.

At 1.7 on the boost charts it puts you right at the most efficient range on both maps where your motor is most susceptible to detonation.

I would be not compare where each map stops on the max flow side of the map as they are from different sources. Both look to be losing efficiency pretty quickly after 400chp with a nod to the GT.

I think that is an old boost map for the 60-1. Based on the new wheel Turbonetics says it will flow more. I suspect there new 60-1 and GTX wheels are closer in technology . If so the 60mm 60-1 wheel should support more HP than the 57mm GT wheel.

I could be miss interpreting this. Just enjoy learning from the exchange and hope someone will correct me if I am going down the wrong road.

As to the exhaust, 3" is always nice but I am guessing that 2.5" is fine in your power range, assuming a turbo friendly muffler, if the wast gate is exhausted separately. Especially if using a smallish hot side for fast spool.

Fun stuff!

Thx.

[RarlyL8]

There is no guesswork with the K27S, it is commonly used in this application. Plug and play. Threshold is 2000rpm on EFI with the J-pipe, 0.7bar in by 2600rpm. Supports 375+WHP.

[Tippy]

Haven't read all post but I have an old T60-1 that with ~0.81 A/R and it doesn't hit a bar until nearly redline in 1st with 930 P&Cs. So, yours doesn't sound too bad. Mine has made as high as 447 to the wheels too.

[lr172]

Originally Posted by 911st

Larry,


At 1.7 on the boost charts it puts you right at the most efficient range on both maps where your motor is most susceptible to detonation.

I would be not compare where each map stops on the max flow side of the map as they are from different sources. Both look to be losing efficiency pretty quickly after 400chp with a nod to the GT.

For the 60-1, my calcs show my flow at 3000 with 10 PSI to be 17 lb. If the turbo spools at 3000, that leaves me very close to the surge line at the 1.68 pressure ratio. I am going to roll the dice with the newer technology, as the T04E doesn't look that bad on the map either. I think there is a lot more to this than the compressor map. I just wish that I knew what all the variables were.

Larry

[911st]

Larry,


Your calc's sound good but I am not sure you need to be concerned about the surge limit.


For reference I know there is a guy here that ran an older technology 60-1 with single BB cartridge on a 3.3 CIS turbo and he was well into full boost by 3k rpm with the stock HE's and a Borla muffler. So I know it is working well by then.

He was at 300ft lbs by 3k rpm which is about 200chp. At your boost that is probably close to 170hp and the 17 lbs you note.

Thus, it has to be well within the surge limit.

I think the K27S, 60-1, GT3076R or GTX3076R if paired with the right hot side are all capable of making a full .6 bar boost on an EFI build like yours somewhere between 2500-3000rpm if that is what you want. They all should support up to 400chp well. Even a K27-7200 with EFI should be at full boost by 3k rpm and support up to 400chp w/o issue.

The main advantages to the non K27's is the ball bearing cartridges and flexibility on the hot side. Once the right size compressor is choosen, it is the hot side tunning that can put the iceing on the cake.

[lr172]

Thanks for the reply. If all of these will spool up at 3K it makes me wonder why I am spooling at 4K with the T04E. It doesn't seem that it is THAT different. I wonder if something else is wrong somewhere.

What are yours and other thoughts on the hot side with this size range of turbo? Is a .63 too small? Should I be looking at the 82?

Appreciate any insight.

Larry

[911st]

The old school K29's on a CIS car spooled at about 3600rpm. Standard bushing, around a 60mm compressor wheel I think. Larger turbine. Made a lot of HP up top.

If I was doing a 3.2 conversion I actually would probably put a larger hot side on it to try to keep the exhaust back pressure ratio down to around 1.5 times boost. This reduces reversion. But I am more interested in track work than low end TQ for the street.

Is your turbo a 60 trim compressor?

What is the exducer size is the turbine wheel?

An .82 should be a larger AR and should spool slower.

Dose your turbo make any odd noise? Have you checked the end play and for binding?

Again, I am still learning about the actual turbos.

Check out this post: HP limit with the stock AFM?

[Tippy]

You have to remember you have a low first gear unlike a 930. Of course your car is going to spool slower than the 930 because the revs come faster and with less load on the engine.

[sjf911]

Originally Posted by Tippy

You have to remember you have a low first gear unlike a 930. Of course your car is going to spool slower than the 930 because the revs come faster and with less load on the engine.

I barely get boost in 1st gear with my 915. It redlines so fast there isn't enough time to spool and 2nd gear usually spins the wheels around 4000 rpm before peak boost. It has always been my understanding that when we are talking about boost threshold and other characteristics of the turbo, we are talking about 4th gear pulls or equivalent. I certainly see a full 0.6 bar by 3000 rpm in 4th gear and it is definately not running out of air by redline the few opportunities I have had to challenge the K27S.

[Tippy]

Ah, yeah, that is pretty bad spool then. My apologies. Mine would make boost almost instantly in 4th at just about any speeds.

[lucittm]

How does your turbo know what gear you are in? Is this a 930 thing? My 965 will boost regardless of the gear selected based on the amount of exhaust flowing out the pipe, which of course is related to engine RPM and throttle opening. The wastegate, which only serves to limit the boost, is controlled by the manifold pressure.

Am I missing something?

Mark

[the_preacher197]

Originally Posted by lucittm

How does your turbo know what gear you are in? Is this a 930 thing? My 965 will boost regardless of the gear selected based on the amount of exhaust flowing out the pipe, which of course is related to engine RPM and throttle opening. The wastegate, which only serves to limit the boost, is controlled by the manifold pressure.

Am I missing something?

Mark

They don't "know" which gear they are in but a turbo takes time to spool. In lower gears the engine increases revs faster so it increases the gap between engine revs and turbo revs (boost).

If a turbo lags the engine by 0.3 secs, the engine may increase revs by 500 rpm in a low gear in that time but only 100 rpm in top gear, hence it appears the turbo makes more boost at lower revs in a higher gear. If you have a very low 1st gear, the engine my get near redline before the turbo gets a chance to spool up.

[lr172]

Last night I pulled the filter off and it appears there is enough wear in bushings to allow the blades to just touch the bore. No significant wear noticeable on the housing. This would explain the slow spool up behavior I am seeing.

I have found a reasonable GT3076R that fits well for my goals. However, it also appears that the map for my T04E 60 trim stage III fits almost as well.

I wonder if it is worth $800 to go with the newer technology and bearings or spend $75 on a rebuild of the T04E. As it relates to spool up, my research is inconclusive on how much of a difference this will really make.

Any thoughts.

Larry

[911st]

Larry,

For $75 I would have to try it.

Did you go the the link in post 13? Might help you decide.