KX Guru Racing

Crofter985:

I've been fence sitting for a while in many ways, one aspect of this was "do I start a build thread?" - "do I not start a build thread".
Well as you can see I've started one, and I've chosen this site as it seems to have a lot of traffic so possibly the most chance of someone who really knows what they are talking about offering a nugget of advice. Here's hoping.
The bike is a 93 klx 650 c1 so it's the electric start type. It's going to get a garrett GT1752 turbo, a keihin fcr 41 carb which is going to be blown through. I have a couple of fuel pumps to choose from and a fuel pressure regulator which is boost referenced malpassi model. I have a AEM wideband, a AEM water/meth injection kit, the water/meth is mainly so I can run a little more boost without messing with the ignition.
I had plans to do a build like this years ago but work and family ensured I hadn't thought much about it until a year or so ago. I bought this bike earlier this year with the sole intention of a turbo project, poor thing, once I pressed the buy it now button on eBay it's fate was sealed. I'm going to try to post pictures on here of how it was when I got it and the work I've done so far.
I've been working on it for a while getting mostly prep work and sorting the wheels, if used the original hubs laced to morad rims, 3.5 on the front and 5" on the back.
The turbo part of the project is just a collection of parts really, I have drilled and tapped the oil filter housing for an oil feed to the turbo and have already tested the oil pressure it was good enough but also when I tested it the engine was cold so I expect the pressure to be less when up and running.

Now this leads on to a couple of oil related questions- I was thinking of putting an oil cooler on the turbo feed line, is this a good idea? Will I lose pressure through the cooler? Will the oil being thicker and cooler arriving at the turbo be an advantage? Would any potential pressure drop be outweighed by the nice cool oil at the turbo? Or is the opposite? I was thinking also of the slightly increased oil capacity not being a bad thing too.

A turbo oil return - I was thinking of welding a chunk of aluminium to the clutch side casing above the water pump gear drive, then drilling and tapping it. But I saw a turbo build on a DRZ400 on here and I think that guy put the oil return through the generator housing, through the plug in the centre of the generator part of the housing. Is this a good idea? Could the engine cope with more oil in the generator side casing? On the KLX the oil returns from the head, down. The cam chain area into the generator housing but I don't think that will be a lot of oil. It probably isn't a lot of oil through the turbo.

agave248:

Some things to consider. It is very difficult to turbo charge a single cylinder engine because of the exhaust pulsing. You are going to need a large expansion chamber to stabilize the charge.

Tapping into the oil fill or a timing plug for the return is far easier than welding on the case. Are you sure the stock oil pump can provide enough volume or do you need an additional pump? If you want to put a cooler on the turbo I would definitely put it on the return line.

I would seriously consider a supercharger instead, its going to be fa easier and fuel injection just woks better than a carburetor. personally I an researching a supercharger fo a TT 350 powered SRX 250.

Crofter985:

How it sat when I bought it.

Crofter985:

Yes it's not going to be the easiest subject to turbo but that's part of the fun. It's always better to enjoy some success if the road to it is a difficult one. I've been reading info on forums and have contacted people who have turbo'd singles and I have got a bit of it sorted in my head, at least. I think I have grasped some of the problems associated with forced induction of a single cylinder engine. I am going to put a large plenum (expansion chamber) on the intake, with a integral tube, like the tube found in front of the air filter on aftermarket induction kits on cars, the tube is also necessary because to get max cooling effect out of the water/meth injection, it has to be sprayed in a few inches before the throttle plate. (Or so it says in the instructions)

The stock oil pump is marginal at best I would say, I spent a lot of time trying to think. Of a way to raise the oil pressure or even mount a piggyback pump of some kind, then I read some more and there have been a few guys who have put turbos on similar engines and it's been ok, so I'm going to give it a go too. I do plan to put some more pre load on the spring of the relief valve, that might help a bit.

As far as supercharging goes, I'm not going to say much about that other than turbocharging is a bit more efficient than supercharging. EFI, you mentioned that too, well I'm not the best with wiring and stuff like that so carbs it is! I would like to think I can get near enough to the correct AFR's with the keihin FCR, it's a pretty sexy looking bit of kit!
Just as a by the way, there was a 40mm CV keihin on the bike when I got it when I put the FCR on it started and ran much better, the FCR is a reconditioned unit bought from a very helpful and polite chap from the states, so hopefully I've sidestepped a problem there.

Crofter985:
How it sits today, or hangs if you want to be precise.
The oil pressure test. This will be the oil feed to the turbo also
The keihin FCR in place.

Matt long

Hi
I've been thinking of doing the same thing.
Having turbo'd a ZRX1100 a few yrs ago, here's my thoughts
I used a Dyna2000 ignition which had an ignition retard setting that was activated by a pressure switch from the plenum
The standard ZRX carb which is not all that dissimilar to the KLX one and was good for 30psi without mods and taking boost pressure and adding it to the breather vents on the top of the carb thus equalising the pressure meant that jetting was within one or two sizes of stock
Oil feed was taken from the behind the pressure switch and gravity fed back to the bottom of the oil pan with no extra cooling
An MSD rising rate fuel pressure reg again reading from the plenum set at 1-2 psi at idle with a return to the tank

I wonder if mounting the turbo by the carb would not only make a cleaner install but effectively create a pulse chamber from the exhaust
Watching with interest
Matt

Crofter985

That's interesting about the dyna2000, is it an add on? Was the unit you got model specific or universal? Who did you source it through?

I am thinking the turbo as near to the exhaust valve as possible is the best solution, the energy of the exhaust pulse only going to get less the further it has to go. Some even recommend lagging the exhaust from the cylinder head to the turbo to limit heat loss as this is seen as energy loss. With the single cylinder the intake pulse is only 1/4 of the cycle so there needs to be a large reservoir/plenum to store charge and even intake pulses, so some extra plumbing on the charge side of the turbo will help that.

It's good that there is interest in the build, it will help the momentum, thanks.

Matt long

The Dyna2000 is model specific, Google them.
In the old days they mounted turbos near the carbs, this was called suck thro as opposed to blow through, the exhaust flow won't dimminsh, it should even out the pulsing though. >popcorn beer<
The Dyna2000 is model specific, Google them.
In the old days they mounted turbos near the carbs, this was called suck thro as opposed to blow through, the exhaust flow won't dimminsh, it should even out the pulsing though

Crofter985

Thanks, I've googled them, dynatec, I see they have a lot of uk stockists. They might have something. That might come in handy.

I was planning to do a blow through setup, all of the research I've done into it points to that method. There has been a few single cylinder builds I've seen that have run well with big plenums and some that ran poorly till they put a big plenum on. A chamber to even out intake pulses, would that work with suck through? Would it give the fuel time to drop out of suspension? Maybe?

I get what you mean about the exhaust pulses evened out but I can imagine the opposing argument too. If you put the turbo as near to the exhaust valve as possible then you get max energy out of the charge of gas escaping from the exhaust port. I also thought of a possible down side to this possibly more heat sinking into the cylinder head, heat that would otherwise be taken away from the engine? Looks like a compromise is in order, again.

I take it your zrx was blow through?

Matt long

Yes, mounted just below the rad.
Ran it for about three years, started at 8psi ended at 15psi, with extra base gaskets to lower the comp, but this just moved the boost band higher up the Rev range and spoilt it.
It was running with ZX10's on the track and putting out about 170 at the wheel.
If you google it it's the blue green and white one with green wheels