Hi everyone! I'm new here. As a short intro, I have owned my MX-5 for 10 years now in Spain and finally decided to supercharge it. So far I think it is working well but I'm not sure about a couple of things and decided to ask the experts here.
My setup:

• 2002 Mazda MX-5 1.8VVT
• Engine rebuild recently
• Megasquirt 3, 640cc BOSCH Injectors and AEM wideband.
• M45 Supercharger from Mini Cooper S with KAVS 17% pulley
• Intercooler with 2.25" pipes
• Dual throttle bodies
• Coolant re-route, upgraded radiator and other non-relevant stuff

I have made a safe tune to test everything and the car is running fine, I can already feel more power. But I want to make sure everything is perfect before taking it to a professional tuner.

My main question is the boost that I'm able to make with this setup. I've read somewhere that the M45 with the smaller pulley should get around 8 PSI but I'm seeing 5.2 PSI maximmum. The thing is that it reaches peak PSI quite early and then it stops rising even if the rpm increases:


The red line in this graph is the MAP and as you can see it gets more or less stuck at 130 kPa (~5 psi) from about 3300 rpm. It seems that I have no leaks and the belt does not slip.
White is RPM and green is TPS.
Any ideas why I'm not making more boost? Maybe Bypass valve leak? It looks fine. Maybe this what you get with the 1.8 and M45?

I have logged some pulls, please let me know if you need me to show anything else.

thanks!

Mark.

 

Welcome Mark, good to have you aboard! You know it's coming, so ... pictures or it didn't happen!

Although my heart said 'blower!', my head said 'turbo', and I went with my head. So I hope others will chime in with more knowledge and experience with supercharging than I.

First thing I would do is thoroughly check for the integrity of the tract, including the operation of the bypass - I note your comment about no leaks but double check it anyway. How do you know you have no belt slip? Have you run the numbers on blower speed with your pullies and compared that to the specs - it could be over-speeding and on the back side of the curve?

You want power, you are not going with that blower, you would be looking for a MP62 or a big Lysholm one. OTOH, that is what you have and so naturally you want to get as much out of it as you can.

 

I'm also a turbo guy and not a supercharger guy but that does seem low for an M45 with a smaller pulley. Are you stock crank pulley or do you have an overlay? What did you do to check for boost leaks and belt slip? A picture of your setup would help as well.