Hi folks,
I have noticed a far bit of intrest in turbo set up's on the A series engine.As I have compleated one of these with great sucess, on a budget, a while ago and I have a few parts left over I am going to build a nother one. When its finished I will put it up for sale. I will post a few pics of it as I go.
It will consist of a dihatsu turbo and will be a blow through set up.
my last one ran 10lbs boost and had standard everything right down to the carby. It worked very well but there was room for improviment so this one should be even better.Ill post a full story on my web page which will be up dated as I go, so you can check it out through the web links.

P.S.Dont be afraid to pass on any tips or room for improviment that you can see....

Im interested in having a go at turboing a spare motor i have but am curious about the charachteristics the motor will have with turbo on cause i dont know a lot of technical stuff when it comes to turbo performance and the pro's and con's of a blow through setup.

Is the car going to be sluggish off turbo because of the setup?
What revs would you expect turbo to hit?
roughly what sort of gain would a stock motor get in terms of power?
would any modifications to the motor make it better suited for turbo application?
what about intercoolers and blow off valves, would they help here or is this not a serious enough setup to worry?
Anything else?

Because of the size of the turbo im going to use it will spool up fairly quickly, its fairly small
But my old set up would rev to 5400 and then loose fuel pressure, it needed an electric fuel pump with a rising rate regulator
Even so it would still go well enough to beat a 6cyl VL comm on lpg(the VL on lpg)

> Is the car going to be sluggish off turbo because of the setup?

Not if you leave the engine stock and just add a turbo. It'll have the same power as before, but when the turbo comes on, it will have even more.

> What revs would you expect turbo to hit?

Same as before. You are limited by the cam and most especially valve springs.

> roughly what sort of gain would a stock motor get in terms of power?

40%

> would any modifications to the motor make it better suited for turbo application?

Yep, same as any other build up - bigger valves, ports, carbs (freer breathing) ... with the big exception that lowering the compression ratio will help. Then you can use more turbo boost on the same octane fuel. On the other hand, lowering the compression ratio will make the engine have less torque off-idle, before the turbo spools up. Depends on what you want -- max hp, or just a boost to your stock engine.

There is a lot to this subject, check out some of the turbocharging Web sites or books at the library.

go_the_datto do you know how many pounds of boost you can run without popping pistons?

next set of questions:

what would be the best head for lowest compresion? (i have a spare GX)

would i be better using the gx head even though i think it has more compression because its better ported and better valves than others?

could i use my twin SU's without boxing them up, or would they also require a box? (it would be good if i could just build a chamber on the air cleaner side of them for compressed air)

is anything like a copper head gasket required, and can this be used to lower compression?

i have a spare fuel pump capable of about 5.5 psi, so how much is a rising rate regulator worth? i bought an adjustable one (not rising rate) for $50 for my rally motor (see in avatar) are they much more and why wont a set pressure one like my other work well?

thanks heaps guys,
Michael

I was running 10 lbs boost in my last set up, But, it was very poorly designed, the exhaust ran very close to the box around the carby making inlet temp very hot,not a good thing but it still lasted about 5000 k's before it went bang.I posted a pic of the piston in the photo section under forum.

The best head would be the one with the lowest compression ratio, the largest chamber.

The S u question Im not sure on. I have seen side draught webbers set up that way on a L20b with a super charger and they worked well

I havent tried a copper head gasket yet but I guess it wouldnt hurt, you could drop the compression the aswell with a thicker gasket.


With a blow through system as boost pressure incresses it tries to push the fuel out of the carby and back to the fuel pump because the whole carby which is inclosed in the box is now in a diffrent atmosphere so to speak.
Your fuel pressure has to be about 3-5 psi above boost pressure in theory, but in practise I found the standard mechanical pump would work up to 10 lbs and 5400 rpm then engine would die for a second then get up and go again and would keep doing that untill you got of the throttle.
Another trick that worked is to pull the mechanical pump appart and streach the spring, it will help.

But ultimately an electric fuel pump and r r reg is the go.I have seen normal regulators modified to become rising rate ones all you do is tap boost pressure into the back of the reg behind the diaphram, Ill try to get more imfo on this or a pic to make it easier to under stand

go the datto, tell us about the motor your turboing on your site, it says 1200 but its painted up and stuff so im guessing its not stock internal is it? tell us here or maybe you should add that to your site. is it getting one or two carbs?

p.s. a couple of people i spoke to have said they think diesel turbos are diffrent and they think cant be used on petrol motors, i know youve done it but is there any truth in what they say

All ive done to the engine is cleaned the ports up a bit, the rest of its stock

about the carbs, Im not sure which way I should yet, the standard carb would be the cheepst but how about making an adaptor and putting a webber of an xe falcon or something like that. Im thinking of going that way because I am trying to stick to a buget but I want it to go well, maby one of a 2 litre cortina they have a webber on em.
I cant decide Any ideas guys??

About the diesel turbos, yer I have herd that you cant have them on a draw through system because the seals dont like the petrol but there ok for a blow through, and I never had any probs with the seals yet

Sorry to join the party so late. As for intercoolers, they are alway a good idea on any turbo setup. (Well, with the exception of a draw through as the fuel will puddle in the bottom and make a nice pressurized bomb, but I digress already.) The nature of gasses when compressed is that the temperature rises. Anything that takes heat out of the intake helps in the prevention of detonation.
I guess I'll have to concede that that does include water injection but I still don't think I totally approve of that. I mean, why waste that valuable space with uncombustable steam when you could put in more air and fuel? Yes it works, but so does a real intercooler and you won't run out of that.
Blow off valves are necessary on a blow through because when you lift of the throttle under boost, the pressure on the top of the float bowl is still high but the idle jet outlets under the throttles are in vacuum. This leads to a "pig rich" situation every time you go to shift. Of course there is the added benefit that the turbo doesn't get hit with a return pressure wave and doesn't take as long to build boost again. Win win situation.
On the other hand, blow off valves are phenomenally bad ideas on draw through systems. Think about it.
For these two reasons, one should abandon the thought of a draw through system, in my opinion.
(Oops, I just thought about it. You wouldn't need a blow off valve on a draw through since there is never a time when the boost side sees a restriction like a closed throttle. Still, draw through is not the way to go.)
As for using the SUs in a blow through system, I don't know what they would do. My initial reaction is they won't work but I have not thought it through enough to give a valid reason.
In the "Box the Carb" vs "Plenum on the inlet" argument, I lean toward boxing the whole carb. That way, all of the passages and gaskets and shafts and such "see" pressure as if the altitude had changed.
With the plenum, there is the potential for the throttle shafts to spew fuel/air mixture or the float bowl gasket to blow out or those little lead plugs to pop out sending streams of fuel onto a hot engine.
Well, that's about all I have to say.