What octane gas should I be running in my MSP?

LowriderS10 · Jul 31, 2015

Hi,

I have a P5 wagon that the previous owner swapped an MSP engine into. He said that it runs just fine on 87 octane and I've read online that the cars are happy with 87. However, Mazda suggests premium. I'm also getting a bit of "chatter" noise every now and again under load...I thought it was valve chatter, but it may be detonation. I started running 89 in it, and even topped up the tank with 94 last night to try and bring the octane up.

Thanks in advance!

mspk2 · Jul 31, 2015

use only 93 in my MSP. I drove one with 87 octane in it and it struggled had to get up to speed. With boost its always better to run a higher octane fuel. Does it have any tuning done to it or is it just the msp ecu in the car?

LowriderS10 · Jul 31, 2015

mspk2 said:
use only 93 in my MSP. I drove one with 87 octane in it and it struggled had to get up to speed. With boost its always better to run a higher octane fuel. Does it have any tuning done to it or is it just the msp ecu in the car?

Thanks! No tuning whatsoever (that's what I wanted). The only modifications from stock are a FMIC in place of the side mount and a CAI. It's running the proper MSP ECU. Performance-wise it's a beast, although it does hesitate a bit under certain conditions at around 3,000 RPM...I'm going camping this weekend, but when I'm going to throw some new sparkplugs and wires at it to see if that solves the problem.

It's also pretty wicked on gas...I got nearly 40 mpg doing mostly highway the other day...I'm rather pleased with that.

704_mazdaguy · Jul 31, 2015

Its going to have the hesitation regardless, the MSP factory tune is terrible. Also dont run 87 anymore, you are def getting detonation. I would run the highest you have, 91/93 depending on where you live

LowriderS10 · Jul 31, 2015

704_mazdaguy said:
Its going to have the hesitation regardless, the MSP factory tune is terrible. Also dont run 87 anymore, you are def getting detonation. I would run the highest you have, 91/93 depending on where you live

Thanks! I'm going to run 91 from here on out...that's usually the highest I can get. It's good enough on gas that I don't mind putting the good stuff in.

Tell me more about this hesitation, please...what's it like on the factory tune? (I just want to figure out if mine's normal or not haha). We put an OBD2 reader on it, and there were no codes (except the O2 sensor bypass, which is a known issue)...so it shouldn't have any problems...though a little tune-up can never hurt (either performance or fuel economy

).

Interesting...looks like this is what I'm dealing with:

http://www.mazdas247.com/forum/showthread.php?123625276-Info-for-the-Reflash

I'm glad to hear that it's a relatively easy thing to solve and that there's nothing wrong with my engine...now...the problem is that it's obviously well out of warranty, and the engine is not even in the correct car haha...

polaris · Aug 1, 2015

If you want to get rid of the hesitation, get a SSAFC or a unichip and relocate your MAF.

callphy · Aug 5, 2015

aluminum hard piping + FMIC would get rid of the hesitation problem, with everything else stock.

i run corksport FMIC， no more hestation after i swapped to FMIC.

believe the 10 years old plastic piping wont hold proper pressure

callphy · Aug 5, 2015

i run 91 octane only

LowriderS10 · Aug 8, 2015

polaris said:
If you want to get rid of the hesitation, get a SSAFC or a unichip and relocate your MAF.

Thanks...where should the MAF go? I'm thinking about the chip, but they're fairly expensive, and since I'm not planning on tuning it, I'm not sure that it's worth it...

callphy said:
aluminum hard piping + FMIC would get rid of the hesitation problem, with everything else stock.

i run corksport FMIC， no more hestation after i swapped to FMIC.

believe the 10 years old plastic piping wont hold proper pressure

Thanks, but mine already has hardpiping and a FMIC and the problem persist...I'll try throwing new plugs and plug wires in it and see what happens.

callphy said:
i run 91 octane only

Good to know! I've been running 91 since the second tank of ownership...

polaris · Aug 9, 2015

Put it between yout BOV and throttle body. Heres how I did mine...

Even if you're not planning to tune, the air/fuel controller will smooth out the rough edges on the stock tune. These MSP's run rich from the factory. It becomes more noticeable the more mods you do to it...

Womb Raider · Aug 9, 2015

I only run premium in my msp.
And i second on polaris. Im running rich af. Could be because a missing O2 though (scratch)

njintau_fsd · Aug 9, 2015

Is your car boosted? If yes, then use 93 octane or you risk blowing your engine due to detonation. But, if its N/A then you should be fine with 87.

hornsfan10609 · Aug 11, 2015

LowriderS10 said:
Thanks...where should the MAF go? I'm thinking about the chip, but they're fairly expensive, and since I'm not planning on tuning it, I'm not sure that it's worth it...

Thanks, but mine already has hardpiping and a FMIC and the problem persist...I'll try throwing new plugs and plug wires in it and see what happens.

That's because the hesitation is caused by the stock tune being too rich, not the intercooler piping.

You may not want to tune your MSP, but driving one on the stock tune is a waste of your time. You may as well get to enjoy the car some

callphy · Aug 15, 2015

hornsfan10609 said:
That's because the hesitation is caused by the stock tune being too rich, not the intercooler piping.

You may not want to tune your MSP, but driving one on the stock tune is a waste of your time. You may as well get to enjoy the car some

if MAF reads big amount of air coming in ,ecu injected big amount of fuel to "proper A/F ratio" and the plastic piping leaks.

isnt that cause the ratio to be rich & richer?

mine has few knock issue before i did all the modding. the car dies during highway ramp acceleration or stop&go at the intersection, slows down on highway when i press the gas pedal

(i was using Costco premium fuel most of the time, and all stock setup)

i quit the job, and spend few months on the car, now it speed up aggresively when i give gas, and never knock or die on accleration （for like a year or two, and i never use costco fuel anymore, run shell or petrocanada 91oct only)

until recently the bolts between manifold and turbo got lose and creates leak and noise...

i am just too lazy to get my hands dirty...

oh just saying, i am still using stock MAF location, run recirculation setup with both BOV and bypass valve (not sure if that helps maintain AF ratio)

hornsfan10609 · Aug 15, 2015

No, the hesitation is from the stock tune dumping too much fuel and the slow computer being unable to react in time.

What octane gas should I be running in my MSP?

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