Car and mods:
1990 Miata
Greddy kit no intercooler with stock piping
Jackson racing fuel pump
stock injectors
Vortex AFPR
Enthuza 3" exhaust
Bailey Blow off valve
Jackson Racing plug wires.
Timing retarded to 4 degrees (Hasn't been verified)
Boost 4.5 lbs

PROBLEM:
In higher gears at higher RPMS I can hear distinct detonation (sounds like marbles rattling around inside the engine)

What can I do to fix this?

 

question:

answer:

 

add fuel.....or subtract timing.

first verify the timing and fuel pressure.
if they look good then i would suspect the stock injectors are not supplying enough.

 

What is the best way to check fuel pressure?

If all looks good I'm guessing I should get some NB injectors?

 

check the timing first.......it's less messy.

 

Hth

 

stop driving like this 'til you figure this stuff out!

 

• Intercooler - Getting one soon
• Vortex Afpr - How do I find out what ratio and what will that tell me?
• Exhaust - What do you mean by Creep? 2.5" DP I think
• Timing - retarded to 4 degrees is the correct position?
• Boost 4.5lbs - Flying Miata boost gauge tells me so...lol. Is there a more accurate way?

I'm driving like a grandfather
I will try and verify everything I am unsure about after work today.

Sorry for my ignorance, this is my first non-stock turboed car and my first Miata. Since I bought it as is there is a lot to learn. I do try and search the garage section of Miata.net and use the search feature here.
Thanks for all your help guys!

 

If the Vortec came with the kit, it's a 12:1 disc.

Boost creep is when boost climbs unwanted, and is sometimes caused by free-flowing exhausts.

Retarded to 6 degrees is actually the right position, but it may not be right for you necessarily.

If the gauge is telling you 4.5 it's likely right, could be wrong but if it was it would probably not read 0 when the car's off.

 

You would be wise to invest in wideband... LC1 if you think you'll ever get an ECU, or AEM (gauge included).

Sometimes a rattling wastegate arm can be mistaken for knock if you don't know the difference.

 

+1

+1

 

Also, what about a bogged up fuel filter, was it ever replaced ?

 

Okay, defiantly buying a wideband, checking timing, and checking for wastegate rattle (tape the rod so there is a cushion?).

I hope it is wastegate rattle...I'd like to go ahead and just buy a new one anyways.

 

I was just looking at buying a new one. OEM replacement is fine?

 

Sure, if your car is a 90 and it was never replaced, just wait until you take it out and turn it upside down

 

would have to be some super high-speed tape to stand up to the heat...

If it is indeed just wg rattle, adjust the rod to take out just enough slack to hold the flapper tight. Although, if the noise only happens at high RPM and during boost, the wastegate should be open, so..?

 

...it shouldn't rattle?
I don't know! LOL

 

maybe it's simply some low octane or bad gas????

 

93 oct always, and it has detonated for several tanks

 

I'm getting off work soon