Hello

I have just bought me an 20b engine that I'm gonna fit into my Rx7FB


I have done some thoughts around buiding the engine to an non seq turbo system before i tune the engine.


Is there someone here that can help me how to do that?


Best regards
Roar Harlem, Norway

 

I don't quite understand, you want to run the stock twin turbos non sequential or are you asking to run it with no turbos at all? I'll help you best I can if I can understand exactly what your wanting to run.

BTW, my last name is Norwegian... :-)

 

cool last name.

I want to run the turbos of course.

I'm just thinking of simplify the vakuum system on the engine.

 

I was looking into doing the non seq with the twins too. Is that even possible? I heard people doing it but how much can you really boost with those turbos ahahha and can we even use the stock ecu?

 

The only way your going to effectively run the 20b seq in another chassis is to do the conversion with the stock ecu and wiring. Now since most of us do the swap with an aftermarket ecu (which most don't have enough outputs to rewire for seq) we convert the turbos to non-seq to simplify the install. The 20b itself has enough low range torque to not even worry about wiring for seq since the Rx7 is much lighter than the Cosmo.

 

I understand.

But isn't there different sice on the two turbos?

If there is, wont the smallest turbo be more stressed than the "big" one?

 

i think the two turbos are the same.... it just boost's at a different rpm

 

hmm, sounds strange, if they hade two simular turbos giving boost at different rpm? why not have only one turbo then?

I tought it was a smaller turbo that maked a low pressure early and one bigger one taking over when it spools fast enough to make more pressure than the small one.

Maybe I'm wrong, but thats what i tought..


Can someone give me a link to a page that explain how to make it non seq?

 

The 20b turbos are different sizes. The primary is larger than the Fd's primary. The secondary is the same size as the Fd secondary. Due to the 20'b added displacement, Mazda went with a larger primary turbo to provide a wider range of boost/flow (which raises the low range torque before transistion) in the lower rpm's before transition. The larger primary keeps the turbo from maxing out too fast. Mazda designed the Cosmo's turbo system to make the power delivery seem v8 like and was never designed for top end power. The smaller secondary is only used to keep up the flow towards the upper rpm levels and keep the torque curve flat ( but it still does tapper off quit a bit).

 

The process is the same as if it were for the fd twins. You wire open or completely remove the larger exhaust turbo control door to keep the exhaust energy from going to the primary turbo. You also wire close the smaller pre control door to help reduce the turbulance and increase spooling. On the y-pipe, you need to wire open the charge control valve. This is the valve that's on the secondary outlet pipe. This valve is normally used to keep the primary charge air from filling the secondary turbo under boost. You need to wire this open since both turbos are going to be spooling at the same time. This is whats called the poors man non-seq. Flow will suffer some but it will still work.

If you remove your turbos and visualize the exhaust air path, you will easily see what I'm talking about. It's not that hard

 

Ok, doesn't sound that hard..

But what will be best? running non seq? or use the system as it is?

is it possible to run the system as it is when i am going to usen microtech LTx12?


I am gonna build the engine to single turbo next winter anyway.
The engine is street ported now and should be able to produce 350 hp at 12-13 psi boost.

what would the people in here prefer to do?