Turbo Newbie needs some info from Turbo Oldies

[Guest]

Recently acquired a complete ray-jay turbo setup for my '78 gs750. It is a single carb draw-through (old Mr. Turbo setup). Going to start the install in the next few weeks. My goal is a streetable turbo with >10lbs of boost. What should the timing (I have a timing light) be set to for this setup? Do I need to add base gasket material to drop the compression for >10lbs of boost. Any recommendations on the oiling system for the turbo itself? Could one of Terrys' (great design sir) oil cooler adapters be used to oil the turbo? Maybe both a cooler and the turbo? Would the addition of an oxygen sensor be required for some tuning purposes? I know there are some turbo racers out there and I'd enjoy and recommendations and tips to ensure I don?t hurt myself. This is my first encounter with a turbo and I'd like to live through the first season and try some more boost next year once the system is running smooth. Are there any other street turbo users in southwestern Ontario? I?m an engineering student working at Ford in Windsor and often drive the 401. Would be nice to see some other Ontario turbo setups to gather some ideas. That turbo was on a 78 gs750 before falling into my possession. Any info/tips will be greatly appreciated.

Mark

[Hap Call]

Re: Turbo Newbie needs some info from Turbo Oldies

Mark, I've never built my own but helped a friend put on on a GS1000 once, and this is what I picked up from him:

What should the timing (I have a timing light) be set to for this setup?

Retard the snot out if it especially until you get it lined out, as much as 20 degrees more retard than the stock setting.

Do I need to add base gasket material to drop the compression for >10lbs of boost.

You need to get your compression down to around 7:1. I'm afraid I don't remember how he figured out the thickness of the base gasket material.

Any recommendations on the oiling system for the turbo itself?

If it was designed for the GS705 application, it should be fine...one problem with GS motors and turbos is that the oil pressure from the engine is not enough for most turbos.

Could one of Terrys' (great design sir) oil cooler adapters be used to oil the turbo?

Not enough pressure if the turbo requires an outside oil supply with pressure greater than 1.5 PSI.

Maybe both a cooler and the turbo?

I strongly advise you put on an oil cooler.

Would the addition of an oxygen sensor be required for some tuning purposes?

No, but it is a nice addition. If you elect not to have it I suggest you make some dyno runs to dial in the fuel mixture.

Hap

[mark]

Thanks for the reply Hap.

I did the math, and to lower the compression ratio down to 7:1 I need to add an additional 2mm of base material (2.0753..ish to be more exact). Does anyone know how thick base gaskets compress to under proper torque? Would I need more than one gasket to achieve this thickness. Spring is approaching and Id really hope to have it assembled and put some miles on the turbo system.

Mark

[marcovandevelde]

Hi Mark,
I'm currently close to finishing my turbo project, although it is a blowthrough system rather than your drawthrough. I've garthered info on turbocharging the GS for almost a year now. For the 1100 the compr. rate should be between 1:7.5 and 1:8.5, I guess for your 750 it is the same. What you can do for the base gasket is to order an ali spacer from Falicon (they do different sizes), coat it with VHT copper spray paint and mount it. I chose to take two Cometic fibre base gaskets and sandwiched an ali Falicon spacer between it, works OK. Order an all copper headgasket from Cometic too, also cover in VHT copper spray paint and mount it. Keep your camtiming (adj. camwheels needed!) and ignition standard if you stay below 7PSI. If you go higher, retard the ign. and/or add water injection. I'm sure you already know to put in HD studs, have a Falicon backplate for the clutch and preferrably have the crank welded.


Keep us informed!

Greetings, Marco.

[robinjo]

Marco what is going to be on the bike after the turbo? Some kind of muffler or nothing?

[marcovandevelde]

Hi Robin,
I'm using a modern type Garrett VNT turbo, this means Variable Nozzle Turbine instead of the old wastegate-control. Basically it has vanes to control the speed of the turbine(exhaust part). Therefore, the vanes are closed when the engine is idling or cruising off-boost, and it will be an effective silencer making the same kind of noise with the short side-exhaust as your kat with 4-1. As an extra I have a quickly detachable straight-through V&H silencer that will be used for even more quiet rides, and then it will be very nearly street-legal. We wouldn't want the cops to be interested because of the noise would we?

Greetz, Marco.

[focus frenzy]

Hi Robin,
I'm using a modern type Garrett VNT turbo, this means Variable Nozzle Turbine instead of the old wastegate-control. Basically it has vanes to control the speed of the turbine(exhaust part). Therefore, the vanes are closed when the engine is idling or cruising off-boost, and it will be an effective silencer making the same kind of noise with the short side-exhaust as your kat with 4-1. As an extra I have a quickly detachable straight-through V&H silencer that will be used for even more quiet rides, and then it will be very nearly street-legal. We wouldn't want the cops to be interested because of the noise would we?

Greetz, Marco.

sorry Marco, I deal with VNT turbo's on a daily basis and these are not remotely quiet at idle, with the vanes closed they sound like a jet engine, and produce a very loud hiss/ whistle.
you are going to need a muffler to keep the joy killers at bay.

[marcovandevelde]

Well focus frenzy,
Then I will put the V&H silencer already on to make sure my maiden voyage will be peacefull!
While we're at it, I believe the VNT vacuum actuator needs to be connected to the plenum, not between the carbs and engine inlet?

Thanks, Marco.

[massakins]

Mark, I installed a Mr Turbo kit on my GS1000 several years ago and have been very pleased with the results. My recommendation is to verify the integrity of your motor and all of the turbo kit components before anything else, then start at low boost and work your way up from there. If I were builidng a GS750 (with good compression, acceptable leakdown and properly adjusted valves) with a Mr Turbo kit (.25 Rajay in draw through configuration) I would first install a Dyna S ignition and coils, HD cylinder studs, copper head gasket, adjustable cam sprockets, welded crank and one step colder than stock plugs. Wiseco or other aftermarket pistons would be prefereable ove rthe factory ones as well. I'd assemble the motor with stock compression, stock ignition timing, set cams at 110in/112ex lobe centers, run 92+ octane gas and keep boost under 5-7#. I found 7-8# of boost to be all a gravity fed fuel system will flow. Get the carb jetted for this and learn to ride it some before going further.

On my GS1000 I used a 10.25-1 Wiseco kit with a .020" lift from an extra base gasket, same cam & ignition timing as above and VP C-16 fuel (adds a lot of forgiveness) at 3psi to make 188rwhp @ 18# boost. After restoring standard base gasket height, changing to .40 Rajay and adjusting boost to 24-25# range it makes 225-230rwhp, but eats head gaskets. The next cylinder has been o-ringed to help allieviate this.

I've run this motor well over 100 passes at the dragstrip and some street time as well with no failures to date. Despite the bad rap the old Rajays get (they are getting harder to find parts for and are expensive to fix) this old school setup continues to provide a lot of performance. Good luck with your setup; email me at massakins@aol.com if I can answer any questions.

[Dink]

Hey Massakin nice to see ya back!
Dink

[AOD]

The late 70's GS's were low oil pressure systems...which means you're not going to have enough juice to force oil in there. You may be able to swap up to a higher pressure oil pump and get by.

Invest some time in making an effecient drain from the turbo outlet as well, that will be important.

~Adam

[massakins]

Dink, thanks for the greeting. Been busy moving myself from the frigid winters of Bangor, Maine to the soggy winter of Seattle, Washington. But, I'm still riding my Bandit now and I never got to ride it in December in the Northeast!

Regarding the low oil pressure of the late '70s GSs, there are ways to make a Rajay live with what they have to offer. Changing oil pump gears is one option (there are two different options here) and the use of a properly placed restrictor is another.

I won't claim to say a turbo will survive idling all day in hot weather but I think it can be made to live with reasonable accomadations. Mine has.

Glad to be back.

[robinjo]

Leon in what way do you have to deal with VNT turbo's ? I never heared you talk about that before.