BMW M2 3.0L I6 and Mazda's 2.5T

[sinistriel@]

The two biggest hinderances to the 2.5t making good power are the size of the turbo and tuning software. Factory turbo is close in size to an early WRX factory turbo for comparison, the CX-50 twin scroll is slightly bigger. Anything over 28lbs a minute of airflow is maxing both turbos out in stock configuration and starts making considerable heat. RPM limit on my car is currently 6300rpm, the engine handles it no problem but the turbo is having issues keeping up.

Mazdaedit just does not have the tables defined needed to control a bigger turbo correctly. We need access to the compressor simulation maps, turbine efficiency maps, P/R maps, etc. If we get that amongst all the boost tables fully and correctly defined then we are dealing with a significant power jump potential. The cylinder head has the flow to support over 400hp, the cams are fairly aggressive for an OEM turbo engine, all the 2.5ts have 256* intake duration, all except the CX-50 run 232* exhaust duration, the CX-50 runs 250*, this is close to the same intake as the 4B11T in an Evo X and more exhaust. Because of the large amount of VVT control we can spool a large turbo relatively quickly.

Better software will enable the next big push in power for the cars.

 

[yrwei52]

⋯ Understanding the level of effort Mazda put into this engine and transmission combo gives one confidence that we have not found its limits yet.

Mazda may have spent some effort to develop the 2.5T based on the SkyActiv-G 2.5L NA mainly for a truck, the CX-9, with the emphasis on low-end torque. The engine will be running out of the breath above 4,000 rpm. But Mazda definitely had missed something on cylinder head modification from the original 2.5L head which could crack caused by the long and heavy exhaust manifold. Mazda did revise the head on the 2.5T to add the structure strength of the cracked area in 2021, and hope the fix would last.

The transmission for the 2.5T? Mazda didn’t put any effort on it. They simply re-use the SkyActiv-Drive automatic from the 2.2L diesel out of the parts bin, with possible different version of TCM software. Nothing special about it.

 

[AL Cx5]

Never is a long time! As an example, the low rev Cummins 5.9 truck engine now revs to 8000 RPM in some racing applications.

I've mildly modify my 2.5T and enjoy it. I have a tune, modified air box with variable flow CAI, grounding and turning vane in one elbow. We also changed out struts/springs/wheels and go 70# of unsprung weight off this piggy cross over. Added aftermarket sway bars with urethane bushings. Lowered 1.5". The car is much more fun to drive, gets better FE and is safer. CX5 engine and turbo work are not on my bucket list.

If the the OP wants more peak HP, much more than a turbo is needed. A different cam profile, intake, fuel delivery and exhaust JUST for starters. I would question the piston and install custom forged slugs. More RPM is needed to make boost/HP. At this point, we don't have transmission tuning. We are stuck at low RPM. If we could wind this little engine up to 8K and had the supporting parts if would scream...

A bigger turbo WILL be slower to spool, or turbo lag. Many of the Cummins guys do compound turbos on street rods. They add an additional turbo is series to the stock or two new turbos. Some of these builds have two high pressure fuel pumps and a larger lift pump. Now we have aftermarket high pressure pumps have been stroked to produce more fuel flow. Don't forget to replace the injectors to handle more fuel flow...

Now the exhaust is going to be restrictive from the exhaust manifold to the tail pipe. ALL of that has to go and be replaced. We have a talented local guy, who specializes in import turbo and exhaust. His stuff is a work of art and costs accordingly. Check out Walker Morgan on FB. He built my custom headers for my race car. An absolute piece of art. Here is a typical turbo build of his. OP will have to get off his checkbook for this mod too....

That is JUST the beginning of the fun. The Cummins guys found out quickly that the flex plate, torque converter, input shaft and other trans components were breaking after turbo upgrades. Over the years aftermarket parts like billet flex plates, torque converters and input shafts have been developed.

I have a billet flex plate and billet torque converter on my Cummins tow pig along with some billet trans parts and performance valve body. These parts help the trans live longer when towing. As an aside, the 47 and 48RE failed OFTEN if the truck had a tuner. My lightly modified 48re went 230K mi and died after some WOT abuse. Today, the highly modified 48RE is THE go to transmission for big power applications. Aftermarket rose to the demand.

Next inline is the driveshaft. They had to be increased in diameter and better U joints. I would then question the CX 5 diff and shafts. I've broken all of these after doing mods on a gas burner. THEN I had to upgrade the bushings and IRS links. Finally the aftermarket produced links for the Dodge IRS. The eBay and other IRS links for our CX 5 are toys compared to what is needed for real power....

As you can see, it's not as simple as changing to a larger turbo, tune it and go. What I found out after going down a similar road, I crossed the point where the car was unfit to drive on the street. It was out of phase with all the other cars. That is, it accelerated so much faster, I was not only on the guy in front of me bumper but his back seat. So street driving was always tense, full attention process. Throw in a cold, wet road and it was a white knuckle affair. That car transitioned to a track only car.

If there is enough interest and people will spend the $$, then the aftermarket will produce the products at some point in the future. 1% of the owners who mod is not going to get much support. Changing turbos is maybe 0.05% of Mazda CX 5 owners...

The OPs goals can be met with enough time and money. In the end the BMW is a better platform for bigger power or a 100 shot of nitrous!

Good Luck!!!

 

[N7turbo]

I'm aware that people can go down the rabbit hole quickly on cars. That's the reason why I have the Turbo CX-5 and not something else I'd be tempted to spend a lot of money on. Been there, done that, not again at this time in my life. For me it's going to be intake, downpipe, and tune, then see how content I am in the 300-350 whp range.

 

[sinistriel@]

I'm aware that people can go down the rabbit hole quickly on cars. That's the reason why I have the Turbo CX-5 and not something else I'd be tempted to spend a lot of money on. Been there, done that, not again at this time in my life. For me it's going to be intake, downpipe, and tune, then see how content I am in the 300-350 whp range.

That is my ultimate goal with my 3. If I wanted to build a track car or make big power I'd pick up an EVO X MR. My goal is 350whp, comfortable, daily driven and reliable.

 

[AL Cx5]

That is my ultimate goal with my 3. If I wanted to build a track car or make big power I'd pick up an EVO X MR. My goal is 350whp, comfortable, daily driven and reliable.

I curious, if the 3 or CX 5/Turbo injectors and fuel pump handle 350 WHP or 420 FWHP?

I roughed it out, using 2900 PSI fuel pressure, it would require about 28% larger injector. Someone would have to research and find a larger injector. I suppose Mazda Edit will scale injectors....

Fuel pump would be in the same situation.

Then fuel lines and other items would have to be upsized to hand the flow.

I know you can handle the converter and trans...

This would be a cool project and hurt a bunch of feelings.

 

[sinistriel@]

I curious, if the 3 or CX 5/Turbo injectors and fuel pump handle 350 WHP or 420 FWHP?

I roughed it out, using 2900 PSI fuel pressure, it would require about 28% larger injector. Someone would have to research and find a larger injector. I suppose Mazda Edit will scale injectors....

Fuel pump would be in the same situation.

Then fuel lines and other items would have to be upsized to hand the flow.

I know you can handle the converter and trans...

This would be a cool project and hurt a bunch of feelings.

No need to change the injectors, we are not at the max limit by any means.