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Old 07-25-2007, 02:28 PM   #1
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Default High RPM rattle--Help!

At about 5k+ rpm on WOT I hear this metallic rattling noise coming from the engine bay. It sounds like there is loose metal bits bouncing around inside the valve cover...
Does anyone know what this sound is? I don't hear it under normal driving conditions, only when I floor it past 5K rpm...
Thanks in advance!
1990 NA Turbo (Greddy)
-Daniel
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Old 07-25-2007, 02:40 PM   #2
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Sounds like detonation. You need more fuel, more retard, less boost, an IC, or a combination of all of the above.
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Old 07-25-2007, 04:04 PM   #3
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Sounds like more retarded timing and injectors...
it currently has retarded 4degrees, it has the Jackson racing fuel pump with stock injectors, 4lbs of boost, and no IC.
thanks
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Old 07-25-2007, 04:15 PM   #4
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Quote:
Originally Posted by BoostedNA View Post
Sounds like more retarded timing and injectors...
it currently has retarded 4degrees, it has the Jackson racing fuel pump with stock injectors, 4lbs of boost, and no IC.
thanks
Wtf. Is that before, or after all that stuff above happend?
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Old 07-25-2007, 04:35 PM   #5
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This is how I bought the car.

"Sounds like more retarded timing and injectors...(<---things I need to do)

(Things it has--->)it currently has retarded 4degrees, it has the Jackson racing fuel pump with stock injectors, 4lbs of boost, and no IC.
thanks"
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Old 07-25-2007, 04:37 PM   #6
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Wow. 4 degrees. Are you running lean? You seem to kinda have the same problems I did.
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Old 07-26-2007, 01:26 AM   #7
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I'm about to pull the spark plugs. I'm not running rich, my 24mpg tells me so! There is a lot of little things I want to do...ie. replace O2 sensor, replace fuel filter, replace plugs

oh, that reminds me, What gap are you using for your spark plugs?
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Old 07-26-2007, 02:34 AM   #8
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I just gapped em myself by guessing. probably stupid..but anywyas, change the fuel filter for sure, and i would consider maybe a walbro fuel pump. next up, IC.
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Old 07-26-2007, 09:19 AM   #9
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gap at 40 and you will be fine. you should not have detonation at 4 psi with the jrsc, or greddy etc. Esp if your timming is 4btdc. i think they recomend 6-8 btdc Is the fuel pump attached to a rising rate fuel pressure regulator. Definitly change the fuel filter and definetly be carefull if you **** with this enough you will kill your ring lands and be forced into a rebuild.
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Old 07-26-2007, 10:09 AM   #10
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WAIT! Are you saying that you're running at 4*retarded, or that you retarded the ignition 4* from stock? There's a big difference. Stock ignition timing is 10*ADVANCED. I think what you're trying to say is that you reduced the timing to 4*ADVANCED, not 4*RETARDED.

Read here for more on timing:
http://www.miata.net/garage/ignition.html

As for running rich, I run 12psi and get 24-25, so mileage in this case is not a good determination of running rich. In fact, if you're only running the stock Greddy kit, only 24mpg would AOTBE mean that you ARE running rich. The stock Greddy kit wasn't engineered to run with a higher-flow fuel pump. So I can almost guarantee you're running rich if you're still on the stock boost. But running rich probably isn't leading to your detonation.

You should absolutely get a new fuel filter, plugs (1*colder please), and plug wires. I wouldn't go with an 02 sensor yet as the engine doesn't use the 02 sensor signal to calculate fuel at WOT... ie, not your problem.

More questions. How are you verifying your boost pressure? You might want to swap in another gauge and check to see if the 4psi you're seeing is accurate. I think the stock Greddy kit is supposed to put out 5psi. If you've got a weak wastegate spring, it might be putting out a little more.

Also ensure you're running the highest octane available to you.
What Greddy disc are you running and what is your fuel pressure (NO FUEL PRESSURE GAUGE?: Look here on how to install one:
https://www.miataturbo.net/forums/se...d=194047&pp=25
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Old 07-26-2007, 11:46 AM   #11
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Thanks a lot guys,
I just bought the car and am still figuring it out, here's what I know about it so far:
1. greddy kit no IC running 4(1/2)lbs (kit installed 4yrs ago)
2. Flying miata boost guage
3. JR fuel pump
4. Fuel regulator (Blue shallow cylinder in front of firewall next to intake manifold with vacuum lines connecting to manifold) <---from memory,don't remember manufacturer.
5. Stock wastegate (not greatest condition)
6. 93 oct always
7. no fuel pressure guage
8. Using stock intake piping, could be getting old and causing boost leak???

Thanks again!
Samnavy- do you fly the E-2c?
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Old 07-26-2007, 03:24 PM   #12
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I do: https://www.miataturbo.net/forums/sh...1&postcount=66
I'm an NFO window licker, so I sit in the back... but it's safer back there.

The AFPR is from Vortech.
Your piping might have a good leak, but then you'd probably also have some rough idling and might be able to hear it leak under boost (maybe).

Is the air filter clean?

I'd say first things to do are:
Verify timing.
Inspect and replace plugs.
Replace plug wires if they're still original.
Replace fuel filter.

It's a piece of cake to put a fuel pressure gauge on the feed line to your AFPR and verify that the stock fuel pump is still up to par. I'd do that too.

If you're going to buy an IC, then don't worry about the stock Greddy piping. Don't forget to engineer a BOV, IAC tap, and Valve Cover Breather Line into your IC setup.

If you don't have the cash for a MS, then a Bipes is almost a must for increasing boost. You'd notice an immediate difference in performance by being able to up your base timing to 14*, and then pulling as much as necessary with the Bipes to combat detonation. Your low RPM power will come back with a vengeance.

A little preventative maint will go a long way to ensuring you don't end up having to replace an engine.

Where do you live? Fill out your profile with your location.
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Old 07-26-2007, 10:05 PM   #13
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Do you have any sort of heat shield? My Bowser one loves to rattle against my down pipe or brake master. Just so happens it only rattles once and a while and always in higher revs. I'd do a quick check of all your heat shields while your at it.
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Old 07-27-2007, 01:13 AM   #14
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the wastegate rod can rattle as well sometimes.
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Old 07-27-2007, 09:04 AM   #15
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Thanks guys, Sam - My Dad flew the E-2 off the Kitty Hawk out of Pennsacola, FL back in the day. Read pilots fly props off carriers!
My heat shield is loose, but I am going to do everything that you say to do Sam, I do have upgraded plug wires (Jackson Racing) and a Jackson Racing fuel pump. I do want to verify what the fuel pressure is so thanks for the suggestion and resource.
The air filter is the stock Greddy POS and I just bought the square to round adapter to fit a K&N filter.
I'll replace the fuel filter this weekend, and buy the IC (w/pipes) sometime towards the end of August (Financial Aid - UCF student Engineering)
What is the MS you are talking about?
Thanks again for all your advice guys! You've made the transition from CrapHonda to Miata seamless. I had one Integra and will never go back to a Honda ever, before that I had a neon ACR and Dodge SRT-4 <--those were good cars.
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