My '71 Turbo Swap Plans

[Cannonball89]

Hey guys, I haven't posted much on this site. I'm usually on Zcar.com but I'm noticing a lack of intelligence over there, so I think I might be on this site more and more.

 

Basically I have 71 240z that is pretty much stock at the moment and I just bought a 280zx turbo with a T5 that I'm going to swap into it, probably over the winter. The motor is a recently rebuilt stock motor with supposedly +/-20,000 miles on it. The head is a P90A with hydraulic lifters. I got the motor running in the car before I pulled it, which wasn't easy because the previous owner went on a wire-hacking spree prior to selling it. I think he planned to heavily modify this car before he realized how rusted out the chassis was. So after about two weeks of pouring through wiring diagrams and doing FSM tests I got the car running on the stock ECU pretty well. A bit of a rolling idle due to some obvious vacuum leaks caused by dry-rotted vacuum lines but I'm going to be replacing all the soft lines anyway, so I went ahead and did a compression test once up to temp and was pleased to find all 6 cylinders at 140PSI except for #5 which is at 135PSI. I think this proves the bottom end to be in good enough shape for a mild street build without rebuilding it.

 

I realize this is not groundbreaking stuff here, it's been done thousands of times. And I have spent many many hours reading old posts on this site trying to get as good an understanding of turbocharged motors as I can. The main purpose of this is just to run my goals by you guys and my plan to achieve them to make sure I'm on the right track.

 

My goals for the car are to have about 300 Lb/Ft of torque at or slightly below 3000 RPM and still be making 300HP up to the 6000 or 7000 RPM (at the wheels). I really don't want to have a car that doesn't have any power until the top end of the band or a car that makes lots of power at low RPM and dies over 5500 RPM. I want a good flat power curve all the way through the usable power band.

 

My plan for achieving this is to first off use Megasquirt. This will make tuning far easier than messing with the stock EFI. In order to make good torque at low RPM I don't want a huge turbo, I think a T04E or T3/T4 turbo is what I am looking for. Something that will spool up quickly to get that instant torque at low RPM and still be able to flow enough air to support the power at the top end. I'm not planning on doing any head porting at the moment, but that plan may change. From what I have seen the stock head is good for 300HP on moderate boost levels. I'm thinking 12-15 PSI should be plenty to achieve my goal and that should keep the turbos I'm looking at happily in their peak effeciency islands. I'll probably be running an intercooler too. I think the key to keeping things happening at high RPM will be a cam change. I think combining a smallish turbo that spools quickly with a slightly hotter cam than stock will give me the torque I want down low and also keep it pulling up to the redline. I think I will have to switch to solid lifters to make it rev happily beyond 6000. Thats not an issue as I have a spare set of solid lifters. I've heard from Tony D that a cam spray bar to replace the internal oiling in the cam will wake up the lazy revving of an L28ET also. That is something else I will look into. Oh yeah, my budget is about $3000.

 

So basically I appreciate any of you that take the time to read this and give me feedback on my goals and my plan. Feel free to tell me if I'm being naive or ignorant. I feel that I have researched this enough to formulate reasonable goals and a feasable plan for within my budget. But I may be wrong. The main thing I'm not sure about is the cam. Is the cam really what I need to focus on to wake up the top end of the motor? Or should I be looking into head porting and keeping the stock cam? Also any recomendations on specific lift and durations?

 

Finally I want to thank all of the members here on hybridz for all the contributions they have made to the knowledge base available for Z cars. I have learned sooo much! Also want to personally thank Tony D for taking the time to talk to me a while back through PM on Zcar.com when I was still deciding what direction I want to go with the car. He really helped me decide to go turbo based on my goals and budget.

[goodoldjam]

 

 

My plan for achieving this is to first off use Megasquirt. This will make tuning far easier than messing with the stock EFI. In order to make good torque at low RPM I don't want a huge turbo, I think a T04E or T3/T4 turbo is what I am looking for. Something that will spool up quickly to get that instant torque at low RPM and still be able to flow enough air to support the power at the top end. I'm not planning on doing any head porting at the moment, but that plan may change. From what I have seen the stock head is good for 300HP on moderate boost levels. I'm thinking 12-15 PSI should be plenty to achieve my goal and that should keep the turbos I'm looking at happily in their peak effeciency islands. I'll probably be running an intercooler too. I think the key to keeping things happening at high RPM will be a cam change. I think combining a smallish turbo that spools quickly with a slightly hotter cam than stock will give me the torque I want down low and also keep it pulling up to the redline. I think I will have to switch to solid lifters to make it rev happily beyond 6000. Thats not an issue as I have a spare set of solid lifters. I've heard from Tony D that a cam spray bar to replace the internal oiling in the cam will wake up the lazy revving of an L28ET also. That is something else I will look into. Oh yeah, my budget is about $3000.

From what I've read and seen 12-15psi isn't going to get the power your after with the stock head. The problem with what you want, is you want alot of low rpm torque without sacrificing high rpm power. I'm running a T3/T4 and I'm not seeing full boost till late 3k rpm, if I was running a T4 exhaust side it would be even worse. You will need to figure out the best combo, my turbine seems to be a bit overkill.

As far as swapping the head for a solid lifter head, I've come to the thinking it's not worth it until I have a cam for the new head that will actually produce power past 6000rpm. That will create even a greater loss in low end.

If you want that instant lowend then keep it stock, if you want HP then go bigger. Either way you go your going to lose out on one or the other. You will have to decide what is more important, you can't be in the sweet spot during the whole rpm range.

The engine will be far less sluggish once you ditch the stock electronics, it's like a wheezing old man who can't breath.

That being said, Finish installing megasquirt and go from there. You'll get a far better Idea of what you want to do.

Edited August 20, 2010 by goodoldjam

[Cannonball89]

Yeah that makes sense. I guess it is hard to get the best of both worlds, especially with small displacement motors. Honestly I'll probably favor more power on the top if I have to choose. I have a blast with the L24 in my car now. You have to rev it to make power.

 

You guys think I would be further ahead to put the motor in my car entirely stock save for Megasquirt and modify it from there? I mean I'm not thinking about pulling the head off of the car yet... so any modifications I'm talking about at the moment would be just about as easy to do with the motor in the car as it would out of the car. Hell even pulling the head off to send it out for porting and such is pretty simple even in the car. Maybe I'll do things one at a time instead of all at once... I don't know I'm not planning on doing anything until the roads are covered in ice and salt lol.

 

By the way, I plan on parting out all the non-drivetrain related parts on the ZX turbo, so if you need something give me a shout.

[Zmanco]

Match the drivetrain to the cam. For example, 300 WHP isn't hard with a moderate cam that makes lots of torque from 3k - 6500 (torque peak in the 4.5-5k range). Match that with a NA 81-83 280zx transmission with a 3.9 or 4.11 diff and once you're above 25 mph there will always be a gear where the rpm will be >3k. Just don't be afraid to rev the motor and use the shifter

[Cannonball89]

Good advice. I am definitely not afraid of revving a motor and using the shifter lol. Anyone with a stock 240z learns pretty quickly how to keep in the power band. I also have a Legends Car (It's a 5/8th's scale stock car looking thing with a 34 ford coupe body and a yamaha 1250cc XJ motor) that I race. The XJ Yamaha engine makes all its power between 6000 and 9800 so I'm not afraid to rev. I thought it would be nice to have a motor that makes power down low like a V8 but still screams at high RPM. But I'm cool with having a peaky motor. It's what I'm used to and what seperates us import guys from the masses of mustang/camaro/chevelle/charger enthusists lol.

[SHO-Z]

Do a search, there have been several members building Supercharged / Turbo cars, using the supercharger for the low end and turbo on top. One was in Europe and was being done because of their laws on swapping engines. I really have never seen anyone complete their project on Hybird. It sound like it could fit your design parameters.

 

Good Luck on the project.

[Cannonball89]

Do a search, there have been several members building Supercharged / Turbo cars, using the supercharger for the low end and turbo on top. One was in Europe and was being done because of their laws on swapping engines. I really have never seen anyone complete their project on Hybird. It sound like it could fit your design parameters. Good Luck on the project.

 

I think that would be the coolest thing ever actually. A positive displacement supercharger combined with a turbocharger would certainly set my car apart from the crowd and achieve my "dream" of a really flat power curve. I allready have some ideas in my head about how to make it all work. Unfortunately thats all that is at the moment, a dream. There is no way my current budget will allow me to do a project like that. Maybe in a couple years after college when I have a good paying job. But for now, I think I will be building a mild street turbo motor that pulls hard at the top end at the expense of low power. I mean it will probably still have more low end power than my L24 so it should still be a lot faster at any RPM than the motor I currently have.