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Tuning turbo and flat top pistons for 10 psi results


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arrang - I am running a 180 degree thermostat at the moment, good to know about the 160 degree thermostat. I just picked up a 3 row aluminum radiator a couple weeks ago but haven't installed it yet. It's on my todo list. Excellent suggestions. I'll add a lower thermostat to my shopping list.

 

six shooter - The sensor is the open GM sensor

 

pyro - thanks :), Im hoping next year for some meth injection maybe. What are your thoughts on a 90 PSI pump? Or do I have to get the expensive 200 psi ones?

 

Ryaapp2 - great read thanks for all the info.

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arrang - I am running a 180 degree thermostat at the moment, good to know about the 160 degree thermostat. I just picked up a 3 row aluminum radiator a couple weeks ago but haven't installed it yet. It's on my todo list. Excellent suggestions. I'll add a lower thermostat to my shopping list.

 

six shooter - The sensor is the open GM sensor

 

pyro - thanks :), Im hoping next year for some meth injection maybe. What are your thoughts on a 90 PSI pump? Or do I have to get the expensive 200 psi ones?

 

Ryaapp2 - great read thanks for all the info.

 

Oh yeah, Also 160* Thermostat and a stock 2 row ZX radiator(which hung low on my 260z)

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Rayaap2,

 

The list of upgrades you posted previously didn't include what turbo you had, Was all that with a stock T3 Turbo?. Wow, because from what I have read on here is that the stock T3 basically turns into a heat blower after 12psi of boost.

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We ran my t3 up to an 18psi peak on the dyno, it wouldn't hold more than 10-12lbs to redline, with every boost increase we picked up torque, power didn't really increase because pressure always dropped back to 10-12psi pretty quickly after peak torque. The power curve ended up as an almost flat line at 270hp from 4000-6000, which leads me to believe that's pretty close to the max this compressor has to give.

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Rayaap2,

 

The list of upgrades you posted previously didn't include what turbo you had, Was all that with a stock T3 Turbo?. Wow, because from what I have read on here is that the stock T3 basically turns into a heat blower after 12psi of boost.

 

 

We ran my t3 up to an 18psi peak on the dyno, it wouldn't hold more than 10-12lbs to redline, with every boost increase we picked up torque, power didn't really increase because pressure always dropped back to 10-12psi pretty quickly after peak torque. The power curve ended up as an almost flat line at 270hp from 4000-6000, which leads me to believe that's pretty close to the max this compressor has to give.

 

I do not recall the exact modifications, but it was basically a T3 with some work to the turbine side. I do remember I ditched the stock wastegate housing completely for a Z31 style one with a larger diameter exhaust integral DP with less angle. And I did have some boost drop off at about 60000rpm that landed around 14-15psi. The exhaust manifold was a stock manifold with some non-professional port work. The turbine housing may have been Z31 turbine housings now that I think about it with a little work done to them.

It was definitely not in the efficient range...

I ran through several stock turbos dealing with cracking turbine housings as well at first. The compressor side was completely stock.

I only ran 24" or so of straight pipe exhaust from the DP.

 

I had expected 14psi to be the end, but it continued to boost higher lbs so I kept going. I daily drove the car with a backup vehicle as the car was $150+$1000 engine swap so it was a lets see what I can squeeze before it goes, after all I had a garage full of spare turbo engines at the time... and somehow Im pretty much there again. The boost really came on like a light switch at those boost levels. There wasnt a smooth transition at all. You never know until you try right.

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Wow glad i found this thread...

 

Im doing a build right now...I rebuilt my stock F54 with P79 head and have about 3000 miles on it and 180 psi on all cylinders.

 

I hate throwing out the pistons and putting in dished with such a good break in on the rebuild.

 

I had talked to a few people in Dallas and they said i would have to pull the timing almost to around 14 degrees if i decided to keep the flat tops.

 

What im wondering is i want to be in the 250 to 300 hp eventually and this is a daily driver so should i put in dished pistons or can this be accomplished with flat tops?

 

I will be controlling fuel and timing with MS-II

Injectors are 440cc

Stock T3

P90 Head

Plugs will be BPR7ES

I was going to start off with j-pipe and stock boost then move to an intercooler and around 10 to 12 psi then eventually upgrade to a t3/4 turbo

 

One more question I just saw a few comments saying that the "A" grind cam is better for this application. I don't have an "A" grind lying around but a have a l26 e88 "C" grind cam lying around would this be even better?

 

nvm just realized that would probably be a pain since my "C" is externally oiled...

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I haven't dyno'd my car but in my opinion 250 to 300 hp should be very attainable. I'd say anything more would be pushing it and need the addition of meth injection. If you havent purchased a turbo already I suggest going right to the t3/t4 turbo right away, I wish I would have...

 

If you have it built I'd say run the setup and see what happens (but then again im cheap). The reason I went with flat tops and p90 was because I couldn't get anymore power out of my f54 (flat tops) and n47 head combo. I didn't want to pay another $1000 to rebuild a bottom end again with only 15,000 miles on it.

 

I've been very pleased with the setup I've got, great power for daily driving.

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Changing to internally oiled isn't that much work, but letitsnow is right, there's not enough "magic" in the A cam to lose sleep over it. The irony is that people have found the A cam to be a better turbo cam than what some of the cam companies sell as a "turbo upgrade cam" for the L28ET.

 

As for making 250-300hp on flat tops. People have done it, over and over again people have done it. Ray just posted results that show he definitely did it. Dump the crappy T3 and step up to something decent and it will come down to if you have the fuel and spark control to handle it. Hell, even back when everyone was going with MS-I people didn't have a hard time absolutely murdering the ECCS EFI in just about every aspect (power, driveability, reliability, economy). And remember BSFC is pretty low, so make sure to give yourself PLENTY of injector. For example, for my dream E85 build I expect to go with AT LEAST 1,000cc injectors that's just to give me padding up to 600 crank hp. I could probably squeeze more out of injectors that size, but I don't plan on it. If I want thank kind of power I'll just step up to 1200+

 

One last note: I've said this before and I still stand by my statement: The flat top + P79/P90 combo has the same turbo HP limits as the dish piston + P90 combo. I say this because I don't believe either to be truly limited by detonation. With both blow up due to detonation? Yes. But remember that the destructive nature of detonation will be similar HP for HP between the two setups, meaning that they should experience the same level of damage from similar levels of detonation at the same power output. Do the flat tops mean you'll have to run less timing? Yes, of course. But don't forget that much of that is a BENEFIT, not a PROBLEM. The flat tops lead to MUCH more quench which will improve mixture and speed up your flame front dramatically. This leads to less time being needed for a complete burn, so comparing time tables of dish versus flat is almost irrelevant. Keep heat under control through the RIGHT size turbo for your HP goals, and run a quality tune and there's no reason the flat tops couldn't make it to 400+hp like the dish pistons.

 

 

 

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Changing to internally oiled isn't that much work, but letitsnow is right, there's not enough "magic" in the A cam to lose sleep over it. The irony is that people have found the A cam to be a better turbo cam than what some of the cam companies sell as a "turbo upgrade cam" for the L28ET.

 

As for making 250-300hp on flat tops. People have done it, over and over again people have done it. Ray just posted results that show he definitely did it. Dump the crappy T3 and step up to something decent and it will come down to if you have the fuel and spark control to handle it. Hell, even back when everyone was going with MS-I people didn't have a hard time absolutely murdering the ECCS EFI in just about every aspect (power, driveability, reliability, economy). And remember BSFC is pretty low, so make sure to give yourself PLENTY of injector. For example, for my dream E85 build I expect to go with AT LEAST 1,000cc injectors that's just to give me padding up to 600 crank hp. I could probably squeeze more out of injectors that size, but I don't plan on it. If I want thank kind of power I'll just step up to 1200+

 

One last note: I've said this before and I still stand by my statement: The flat top + P79/P90 combo has the same turbo HP limits as the dish piston + P90 combo. I say this because I don't believe either to be truly limited by detonation. With both blow up due to detonation? Yes. But remember that the destructive nature of detonation will be similar HP for HP between the two setups, meaning that they should experience the same level of damage from similar levels of detonation at the same power output. Do the flat tops mean you'll have to run less timing? Yes, of course. But don't forget that much of that is a BENEFIT, not a PROBLEM. The flat tops lead to MUCH more quench which will improve mixture and speed up your flame front dramatically. This leads to less time being needed for a complete burn, so comparing time tables of dish versus flat is almost irrelevant. Keep heat under control through the RIGHT size turbo for your HP goals, and run a quality tune and there's no reason the flat tops couldn't make it to 400+hp like the dish pistons.

 

There is one notation about flat tops vs dish that has not been covered in this thread. Turbo dish pistons have more meat and strengthening in the piston itself. Its minor stuff, but IMO Nissan took the time to do what they always use to do back in those days and over built the holy living crud out of it. There is a thread buried in this site showing the differences. It may possibly be a sticky somewhere I do not remember.

The reason I went with the flat top F54 motor was because I destroyed the stock turbo bottom end in short order with the first untuned green build. By green I mean my personal experience as a technician/builder/tuner. All six pistons had broken ring lands, broken rings, cracks up either side of the skirts and showing significant wear on the thrust surfaces. That motor was a true garage trophy of my greenness. The non-turbo blocks were plentiful and cheap(Free-$50 a short block).

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I agree 100% with Gollum's latest posting...

I was 'dial a boost' between 275 and 350, which eventually led me to the conclusion that really the TurboXS two-stage controller is perfect for a street car. It was either 'daily driver' or 'oh, the Honda wants to run does he...' setting...dry.gif

 

"The power curve ended up as an almost flat line at 270hp from 4000-6000, which leads me to believe that's pretty close to the max this compressor has to give"

I would agree with this. If you look at the compressor curve you are in stonewall for the PPH the wheel will produce. If you had a sensitive enough piezeo pressure sensor, you would see pressure fluctuations in the plenum or dishcarge pipe resulting from the intake valve opening and reversion waves influencing the pressure. The turbine speed is over optimum.

This same phenomenon was experienced by JeffP on his larger turbo. Made the same HP at 7200HP an 17psi as he did at 25psi and 6875.... from each of those points the HP just "flattened"

He would not turn it down to 15psi, and run it to 8500 to see the cam power point. From THAT test alone you can see what advancing/retarding the cam will do to put your power point, stonewall point, and upper rpm limit all in the right perspective.

And it also tells you that you don't necessarily have to run a lot of boost all the time, you CAN up the R's. The A-Cam will run to 6500 as you can see. Which is nice compared to the stock boring turbo cam at 5800 so if you are road racing it will make for nice stuff on the straights if you gear correctly. But like stated, it's not a big deal to get in a twist about. And yes, the irony of a stock N/A cam being 'better' in the application than many aftermarket cams supposedly 'tailor made' for the situation tells you something about the marketing and myths involved in the automotive world.

When you talk to Ron Iskendarian, or even read their catalog it will state: "Duration and Timing same as stock, more lift." -- it's a couple 'Stages' down the road before Ron alters event timing. First is more lift. It's a 'freebie'---same driveability, more power, maybe slightly less valvetrain stability (but not an issue at only 6500!) EVERYBODY in the VW world running a bare bucks turbo was putting 1.25 ratio rockers, or 1.5's on in order to get more lift and duration than the stock cam gave. The power change was definately quantifiable, and your driveability was identical to stock.

I digress...tongue.gif

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"That motor was a true garage trophy of my greenness."

Tradition demands a single, worst example of the failure be preserved, and placed on a shelf. "Offerings to the Gods of Speed"....

I watched that documentary when I was 6 years old, and somewhere that phrase stuck in my mind, to be put on MY shelf.

Not until I watched the "World's Fastest Indian" on DVD, and saw the Documentary did it click in my mind where I'd seen that phrase, subliminally registered, to be used almost 30 years later!

Everybody who is serious has 'The Shelf'... if you are pushing the envelope, you will have plenty of examples. I'd need a conex box if I kept WHOLE ENGINES!

Hanging from my rearview mirror in my 62 Microbus to this day is a mangled M12 flat washer, suspended on monofilament line.

It's a reminder that 'when you rush, and you are missing something, DON'T ASSUME it's on the GROUND beneath that engine you just installed...'angry.gif

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Just curious if you ever did try a colder plug. Plugs make a big difference in a turbo application for the L28ET.

 

I would also put some more effort into the air flow to, through and past the intercooler and radiator. Your intercooler is a thermal capacitor and at speed you should be bringing your temps down significantly when not under boost. The Spearco probably has twice the thermal mass with it's cast end tanks as a typical ebay intercooler. You should be ahead of the curve not behind it.... ducting and placement of the intercooler is what I would investigate. You're running MS so you already have the tools to see what difference mods will make.

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"That motor was a true garage trophy of my greenness."

Tradition demands a single, worst example of the failure be preserved, and placed on a shelf. "Offerings to the Gods of Speed"....

I watched that documentary when I was 6 years old, and somewhere that phrase stuck in my mind, to be put on MY shelf.

Not until I watched the "World's Fastest Indian" on DVD, and saw the Documentary did it click in my mind where I'd seen that phrase, subliminally registered, to be used almost 30 years later!

Everybody who is serious has 'The Shelf'... if you are pushing the envelope, you will have plenty of examples. I'd need a conex box if I kept WHOLE ENGINES!

Hanging from my rearview mirror in my 62 Microbus to this day is a mangled M12 flat washer, suspended on monofilament line.

It's a reminder that 'when you rush, and you are missing something, DON'T ASSUME it's on the GROUND beneath that engine you just installed...'angry.gif

 

HAHAHA...

 

I have a large box of trophy's that use to be displayed on my work bench. Everything from L-series to BBC. My favorites are held together with silicone. One particular BBC spun a bearing and tossed the rod during a really good burnout(it was 454 in a 72 Z). There is about 1" of rod that is just missing right in the middle. There wasnt a chunk to find either! That was the last running BBC I owned to this day.

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  • 5 weeks later...

What cam are you running? I have been running my flat top P90 turbo for 5 years now with great results on the stock ZXT EFI. Granted, not much is stock accept for the bottom end, but I think cam selection for the higher comp makes a difference. I have a mild Delta Cams turbo regrind. If you don't have it already, you may want to consider at least the 'A' cam.

 

Aaron

 

Would you suggest using a "C" cam out of a 260z e88 head cause my p90 came back from the shop with a crack around the dowel for the timing chain gear. How much does Delta Cams charge to regrind a cam?

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