advice on old school turbo 280z

[rossman]

I recently purchased a '78 280z with a custom bolt-on turbo set-up. The system was designed by Bell Engineering in the early 80's. It has a Rajay R70 turbo with custom piping, variable rate fuel pressure regulator, modified NA exhaust manifold with a diverter to the turbo and welded on fitting for the external wastegate. As far as I know, everything else including the FI is stock NA hardware.

 

The previous owner purchased the car with a broken connecting rod. He rebuilt the engine with Nissan .020 over turbo pistons and used the stock NA head (N47). The stock NA injectors are clogged (it sat for a while) and the down pipe is rusted thru. I checked the turbo shaft by hand and it does not have any perceptible play. I did check that the car will run by installing some old leaky injectors that the PO gave me with the car.

 

Just looking at the turbo it seems really small which makes sense since the system was designed for an NA engine. The turbo setup was designed for a high compression NA engine but now it has turbo pistons. It seems like that the turbo will have to flow quite a bit more to get significant boost and this may put the turbo out of its efficiency range and lead to detonation. This is especially bad since the setup does not have an IC or water injection.

 

I was hoping to get 200+ HP out of this car. I am trying to decide if it is worth my time and money to get a new custom exhaust installed and attempt to tune up the car with the turbo setup "as-is."

 

Thanks,

Ross

[RTz]

Welcome Ross,

 

I see some 'red flags'... but I don't see any questions. What (specifically) are you are asking?

[rossman]

Sorry I guess I rambled a bit. Do you think I could make this system produce ~200 - 225 HP without significant risk of detonation? I plan to eventually design a custom 300 - 350 HP turbo setup so I don't want to destroy the engine.

[proxlamus©]

dont need a "custom" setup for 300-350rwhp..

 

this is easily obtainable with a stock block and cylinder head.

 

Bolt on a larger turbo.. bigger injectors.. nice intercooler and a good EFI management.. your in the game

[RTz]

Do you think I could make this system produce ~200 - 225 HP without significant risk of detonation?

 

Offhand... NA motors, on stock cams, can make over 200hp. Unless your turbo resembles a cork, I don't see why not.

[rossman]

Bolt on a larger turbo.. bigger injectors.. nice intercooler and a good EFI management.. your in the game

 

To me that is a custom set up. I guess you mean I don't have to do any custom engine work. This is good news, I really wanted to avoid it.

[rossman]

Offhand... NA motors, on stock cams, can make over 200hp. Unless your turbo resembles a cork, I don't see why not.

 

I guess my expectations may be little low. I may install a wide band and just start tuning it to see what I can get.

[myplasticegg]

I guess my expectations may be little low. I may install a wide band and just start tuning it to see what I can get.

 

Save the wide band money for now and use it on some dyno time.

[rossman]

Save the wide band money for now and use it on some dyno time.

 

Good idea, thanks.

[slownrusty]

Lets see some pics! We are a visual bunch over here at HybridZ!

 

Yasin

[rossman]

Here ya go! http://picasaweb.google.com/rossharold/OldSchoolTurbo280z

[pjo046]

I had a rajay-turbo like that on my previous Z(260Z 2+2), and it was good for about 250hp. I had a fmic though, and a piggyback controller and two extra injectors before the TB, in conjunction with the stock L28 efi-system.

The car pulled good from 2500rpm and onwards, I hit peak boost(14 psi) at probably 3700-4000rpm. But in the long run this wasn't enough power for me, combined with my need for a coupe instead of a 2+2, so I sold the car and has been working on my next project ever since.

 

If I were you, I'd get hold of a cheap OEM exhaust manifold and buy a new T3/T4 hybrid turbo and take things from there.

[rossman]

Thanks pjo. Yeah I don't know if I want to invest too much in this system.

[rossman]

I added a picture of the exhaust manifold adapter and oil return.

[pjo046]

I see. But if you are planning on building a proper engine out of this in the long run, you can still use the T3/T4 hybrid when that time comes. I have a T3/T04B hybrid custom made by James Thaggard, and that turbo is good for 450hp. I'd rather dish out some money for a new turbo and exhaust manifold than upgrade the exhaust system if I were you. But then again, using the system as it is now will probably work fine as well. But I wouldn't start upgrading the exhaust if you might have to change it in the future anyhow.

[dj paul]

if your happy with 225 then stick with this setup. that is one of the few times ive seen one of those and the only one ive seen that someone has at the present. there is a compression ratio calculator around here somewhere but i dont think your compression should be too high since you have dished(turbo) pistons. I think it would only be around 8.5 with your setup which is pretty much stock turbo CR. But if you do want more power, simply go with a bigger turbo and stock turbo exhaust manifold with better DP etc. since the CR is lower and it was designed for NA motor then that means you can turn up the boost to about 10-12 safely and even higher with a cheap cold start valve mod. (i think) lol

[pjo046]

Stock turbo CR is more like 7.5:1 than 8.5:1.

[rossman]

Thanks for your replies. I have decided to go ahead and upgrade. As pjo suggested it would be more economical than spending money on a custom exhaust for this turbo when I plan to upgrade anyway. So, I took that advice and purchased a turbo exhaust manifold off ebay earlier this week. Now I need to decide between a Holset HY35 or a T3/T4 turbo.

[pjo046]

I'd go for the T3/T4 hybrid if I was you. I think this will give faster spoolup compared to the holset, and thus better driveability on the street. The holset is better for top power, but as you are only shooting for around 350hp, the T3/T4 is more than up for the job.