What is the maximum boost one can run using an MSD boost retard unit?
What should I set the base timing to before I install the MSD unit?

 

That's a pretty vague question. Here are a few variables that will effect the answer to your question:

• Whether you're running intercooled or non-intercooled
• What kind of fuel control you're using
• what octane fuel you have available to you (93 vs. 91 vs. ?)
• The climate you live in (hot vs. cold)
• the effectiveness of your cooling system
• whether or not God is happy with you on that particular day

Short answer - it's kind of trial and error. You won't know until you carefully experiment. if it's pinging at 12psi, you need to either dial back boost or set your base timing a couple degrees lower. I'd start at static 10 degrees advance at 8psi and increase it by small incriments until you find your happy place.

 

It's a 90 1.6, I have a 16g turbo, intercooled with a walboro 255gph fuel pump, with and electric oil pump to drain the turbo back into the block, custom dual exhaust with free flow mufflers, stock injectors, currently running 5psi. I live in MA.
I am planning on purchasing an MSD boost retard unit. And just wanted to know how much boost could I safely push? And should I set the timing at a specific number before adding the MSD unit?

 

timing isnt the problem, its the fuel pressure with those injectors.

 

the max retard is like 6* IIRC. I wouldn't be looking to break and records, but with a base timing of 10*, you could push the boost a bit...you'll still always be limited by fueling and other factors anyways.



off topic: why do you have an electric oil pump!? is your turbo under the trunk?

 

I have an AFPR set to about 50psi at idle. Which I understand will increase when under boost. I have an electric oil pump in my engine bay from shurflo because the way the turbo is set up, gravity really didn't help with proper oil drainage. So instead of tapping the oil pan I use the pump and an oil cooler, then feed the oil back to the valve cover through the oil cap. Though the turbo is also liquid cooled, I figured it would be wise to cool the oil before and after the turbo. I used a similar set up in my 1990 300zx rear mount turbo. The car currently runs great, but I know that the MSD Retard unit would be wise to use. I just want to make sure that if I increase boost to 6-10psi that i don't hurt the engine. I tried using 315cc injectors from a supra but the engine was flooded by the injectors and ran way too rich. So I figured I try the msd kit because it's way cheaper then a MSpnp.

 

well, if you're running 50psi at idle, there's a reason you're flooded with fuel with 305s I assume you don't get the best gas mileage with stock injectors installed either....

 

When I called the local Mazda dealership I was told that The stock psi on the miata is 46-78psi on the feed side. If I ran an AFPR @50psi on the on the return side what difference would that make? And by the way the AFPR was not installed when I tested the 315cc injectors.

 

what AFPR is it? did you remove the stock one?

stock fueling is 35psi at idle and 48psi at atmospheric, WOT. 1:1 in boost after that.

at 14psi of boost, i've just hit 60psi of fuel.

this is 90-97 of course. 99-00 is 60psi no matter what. 01+ dunno.

 

I have it hooked up after the stock fpr on the return line. At idle it's reading 50psi. Fuel mileage has not been an issue. Should it not be that high?

 

you should retain 35psi at idle, and tune for 50psi at 0~hg. then tune the pressure in boost based on your boost level and injector size.

I suggest you read my FAQ in the DiY section.

https://www.miataturbo.net/forum/showthread.php?t=4288

 

What brain said, im idleing 330 cc injectors fine, your pressure at idle is wayy up.

 

What kind of spark plugs are you running?

What type of AFM, stock or RX-7?

Have you pulled the spark plugs out to see how they look?

A friend had tons of issues with his turbo BP and a AFM RX-7 swap worked it out amazing.

 

The MSD box is better than nothing, but don't pay more than $75 used for one, more like $50. The bipes is a better option for a few more bucks.