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calling all high compression turbo


DAT240Z

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I have a 240zt running all stock 83 turbo system at 10 psi.

This winter I would like to build me a flat top turbo motor, Now I have read a lot on this and from what I gather most say this is not the best way to go. However I want to give it a try I know there are others that have built this turbo combo, what I'm looking for are those that have done it or have knowledge of this build and what your experience have been. What the most boost you have run on stock management system.

MY goals are to have a car with good acceleration as well as top end performance 250wrhp to start with and then when I get some money get

a T3/T4 turbo and than look to make 300wrp.

 

This is what I looking to build.

N/A block

p-90 head (This combo should be 8:5:1)

turbo oil pan and oil pump

turbo distributor

supra intercooler

blow off valve

t3 turbo

10psi boost for now (370CC injectors and SDS in summer of 05 then hope to run 15psi)

up grade clutch not sure what brand yet so if anyone have some suggestions I'm all ears

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all I have to add tothis is that 8.5 compresion is NOT "high compression" for a Turbo Application, and in fact I believe the general consensus will be that it is the ideal compression ratio with which to start!

 

If you want "top end performance" ditch the stock manifold---it hinders you above 5500...

 

Other than that, 250 tothe wheels will be a breeze to achieve. 300 will take some work, but you might consider Megasquirt2 when it comes out...

Eventhe basic Megasquirt-n-Spark program is loads better than the stock ECU in terms of throttle response and fuel mileage off-boost.

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I have 8.9-1 compression for my setup. I have to tell you that it PULLS SO FRICKEN HARD FROM THE MOMENT "GO"!! :twisted: That's with stock boost too.. Yesterday I bumped the boost up to 8psi after programing the settings in my SDS. I thought something was gonna break! :shock: the torque is insane.. I heard a "click,click" sound in the engine bay and at the moment I thoguht it was "ping" and shut the boost controller off for the rest of my trip. I was too far from home to have any real problems. While heading home and reliving my 8psi experiance over and over again. I realized that the "click, click" sound was the boost controller solinoid and not "ping". This weekend I will be doing some more tuning and setting the system to run a solid 8psi as my "low" setting all the time. At the sametime I will be setting my "high" setting to 10 psi and tuning for that.

I built this motor with stock Nissan parts. Who knows how long it will hold together or how much boost it will take. I believe that the key my setup running so well is the SDS system and everything being balanced.

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Yeah I will be posting my maps and updates as I make changes. I'm still working on the map. I need to make adjustments to the tempature settings cause the weather changed this week to much colder then it was last week and I noticed the mixture changed to being kinda FAT. I also have to make a few changes to my map sensor settings, in the vacume ranges. When cruising I can run a little leaner..

 

 

 

I just installed a 6 puck ACT. Before that the stock turbo clutch would not hold as the RPM's came up. It would slip at about 4000 RPM's under a load. At the sametime I installed a SPEC aluminum flywheel.

WHAT A COMBO!!! I will be buying the same setup for my other turbo build.

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Guest bastaad525

I think Tony D hit the nail on the head. So many guys on here look at anything over the stock L28ET's compression as being 'high compression', but really, if you look at any modern turbocharged car, they are all in the mid 8:1 area, and some are even into the 9:1 CR range.

 

With good fuel and spark control there should be NO problem running a turbo on a 8:1 CR L28. However, it seems to me 'the bottom line', the final, highest amount of boost you could ever run, would be limited by running the higher CR, but really.... chances are you would never run your car at that boost limit anyways, or even at the new, lower boost limit of the higher CR.

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I will cross pollinate a thread here from another forum and mention to Bastaad that I witnessed JeffP's car on the dyno smoke his CF clutch at....

 

 

 

 

 

are you ready for this?

 

 

 

 

 

"About 4000 rpms"

 

SOUND FAMILIAR?

 

Got a good idea where PEAK TORQUE might be in a turbo Z? If Pallnet built his engine from Nissan parts, and JeffP has a radical cam, and all custom stuff and they both fry the clutch around 4K, you gott a know there is some sort of "characteristic curve" to a turbo Nissan L-Engine.

 

I bet you look at your dyno graph now, and go "Hmmmmmmmm, no shi...." :lol:

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the highest boost limit is limited by the INTERCOOLING.

if you can perfectly or better than perfectly intercool the charge air, you can compress it all you want.

Staged Turbocharger systems in Tractors run 100+PSIG!

If you crank in a turbo of 30psi and cool it to near ambient, it acts like ambient air when you compress it, that is to day with no detonation...

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Guest bastaad525

but out of curiosity what engine compression do those tractors run :D

 

 

I think when most people talk about problems running higher compression they are usually thinking in terms of stock efi/ignition. As long as you have a way to up fuel and, probably more importantly, retard spark, you should be fine. IF I ever build another motor, I would like to go with flat top pistons in that... the stock L28ET is a dog off boost and it's annoying. I THINK I could get away with the higher compression by the simple addition of a boost-timing retard unit.

 

 

Tony - yes, my torque peak is at 4000rpm. Well, actually it peaks at 3000, and stays very flat to 4000. I wish I still had the dyno sheets for my N/A motor for comparison, but I gave them with the motor when I sold it. I remember it had a very nice, flat torque curve, and only got better after I installed the hotter cam.

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the highest boost limit is limited by the INTERCOOLING.

if you can perfectly or better than perfectly intercool the charge air' date=' you can compress it all you want.

Staged Turbocharger systems in Tractors run 100+PSIG!

If you crank in a turbo of 30psi and cool it to near ambient, it acts like ambient air when you compress it, that is to day with no detonation...[/quote']

 

 

Are you trying to say that if I could cool 40 to 100 PSI I could run it in my car? I really have a hard time in following this line of thought. If this were true there would be drag racers ie.. Honda guys running 100 psi on the track. No dought intercooling has a huge effect on the performace of a car. I just can't see it allowing you to run any boost you want as long as it is 99% or so effective. We would also see guys with intercoolers as big as thier hoods if this was true.

 

Not trying to flame :D here but, I think thats altittle misleading.

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You are only looking for 300RWHP, so unless the engine is in bad shape, why bother rebuilding it? Freshen up the head with a 3-angle valve job, do some mild port matching, ditch the Supra I/C and invest in a good I/C and DP and tune, tune, tune. You do not need anything more to reach your goal if you have an SDS, injs, upgraded turbo, good I/C and exhaust.

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Im just plumbing my intercooler at the moment, but i have built up

using NA Block and other bits not mentioned.

P90 Head port matched.

NA cam from the l28

370cc injectors

3 inch dump & exhaust

Autronic fuel and spark engine management.

t3/t4e turbo.

240mm clutch

Flattop pistons

8.3:1 CR after a bit of machining on the head bores etc.

I plan to start at 10psi boost and finish at 15psi.

I get 98 Octane gas here.

 

I havent turned the engine over yet. But I reckon I can tell you how it goes in about 2 weeks or so with a light tune to run it in.

Will let oyu know how it goes.

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Thanks guy,

There's a couple things I forgot to mention about my current set up

I have one of Scotties G's downpipe and 3" exhaust my engine has 75kmiles and runs just fine. I wanted a bit more off the line accelerations and more HP that's why I thought building a bit higher compression engine would be the way to go with a T3/T4 turbo. I was playing around with the Lengine program and found by replacing the 90a on the turbo block with a N42 and Felpro gasket the compression would go to 8:5:1. Would this be a better way to go, would I get the off boost responds I'm looking for?

 

I guess what I'm trying to ask is by replacing the dish piston with flat top or just replacing the head with an N42 both will give me 8:5:1. will one pull and respond any different than the other? if so can you please take the time to explain

 

Scottie, you segregated a better intercooler, which one would you recommend?

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What's the chances of this: Heres' James T's Twin Turbo Dyno chart he just posted over at ZC.C on aonther topic.

Please note peak torque and when it occurs:

 

dyno1.jpg

 

This would tend to make the clutch very unhappy, especially if you have on that is dependent on flyweights to clamp it down at higher rpms... 8)

 

But uncannily it's near 4200, right at the magic peak point for most of the other units.

The graphs should cross at 5252rpm. If they dont, or peak HP occurs before that point, something is wrong in fueling or camshaft selection!

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Guest bastaad525

Jonzer - I think he's saying if HP peaks before that point there is a problem. And when I dynoed on a Dynapack dyno, the hp and torque did not cross at 5252... The shop guy could not explain why this happened, rather, he wouldn't even except that this was a 'problem'.

 

 

Tony - You say that if my hp is peaking before 5252 rpm there is a problem with fueling or camshaft selection. Well I'm running the stock cam, which hasn't seemed to limit anyone else from making peak power higher up in the revs, and as far as fuel, I have enough *shrug* if that's what you mean. A/F ratio is in the low to mid 12's up above 4000rpm...

 

So how does this account for my low hp peak? I'm still thinking it's a problem with the exhaust, but then again, even the system I"m running is better than a stock exhaust system... larger pipe and no cat, with a straight thru glasspack as a muffler, so my exhaust must be less restrictive than stock. And I know even stock cars make their peak power at a higher RPM than my car.

 

Which has me thinking that when I do go with a full 3" mandrel system this may not even solve the problem and that will leave me stumped.

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