MX5 with M45 supercharger woes (Megalog file included)
 

Hi all,

New user here. I'm really suffering with my MX5 and I'd really like some pointers.

The car: MX5 NA 1800
Boost source: M45 (from a mini) 67.5cm pulley
Setup: Dual throttle bodies, down and around intercooler, TDR 150mm pulley, Megasquirt V2, 450cc injectors.
Issue: Lack of boost.

So I have installed the SC, intercooler, megasquirt and injectors and I was getting the whole of 3.5PSI of boost. I then bypassed the intercooler and found that I was getting closer to 5.9PSI. I checked for boost leaks, couldn't find any, so I installed the 150mm crank pulley with the intercooler and I ended up with 5PSI.

As you'd imagine I was very disapointed so ended up purchasing a boost leak tester which I found was loosing boost at around 5.5 PSI - so I sorted that problem out.

Now the maximum PSI boost I am getting is 5.5PSI boost with everything attatched, the system not leaking any boost (apparently).

I have also installed new O rings on to the injectors and blocked off the EGR valve.

So miataturbo, is there anything I'm missing? Is there anything more that can be done?!

I have also included a Megasquirt log of a run earlier today if that is of any help?

Cheers,

Allister

install a turbo run all of it?






certain your belt isnt slipping?

Are you certain the m45 isn't worn out? When they are worn they don't make pressure.

Yeah I'm thinking about turboing now!

Yep, 99% sure there is no slippage I'm running a 6 rib belt bloody tight!

Other than the boost issue are there any other tell tell signs?

Scoring or marks along the inside walls of the supercharger case or the tips of the rotors. Should be smooth and polished with no scoring.

there will always be some scoring on the rotor tips and in the blower housing, the only time that there isn't is when it's brand new and never been used....

Have you checked your timing belt?
May be a tooth (or 2) off, with massive overlap.

The m45 is pretty small for 1.8, is it even supposed to put out any more than that?

What is vacuum at idle?

Do you have a check valve in your IAC hose? My M45 on my 1.6L makes 7 psi reliably at full boost, stock pulleys.

my m45 makes 6psi with stock crank and a brp pulley(about the same size as stock), single throttle body, AFPR, begi timing control, and a stock 4 rib setup. Its been a reliable daily for 12 years. Don't sell your s/c setup, just set it up right! At idle you should be at a steady 17 psi of vac. if i were you i would check the bypass. Here is how Good luck with your headache!

P.s. i'm not running an intercooler, since you are you might be experiencing significant pressure drop across the intercooler. I doubt that's the whole problem, but it will reduce the boost pressure slightly in the end.

Take a look at the valve that bypasses air
from the sc outlet to the sc inlet (it has a vaccum actuator) you will have low boost if it is worn or not closing all the way.

What type of Intercooler are you using? If you installed one of those giant Ebay intercooler, you will loose 1.5 to 2 psi. My 1.6, M45, and overlay pulley without intercooler runs 8PSI. With Mazada speed stock small intercooler, I am now running at 7PSI.

Also, check you hose going to the boost gauge, all it takes is a small leak of crack on hose resulting false boost and vacuum reading.