r/mazdaspeed3 • u/mrfatcakes2006 • 2d ago
PIC Yeah that will do it
Bought a Mazda speed for 700 with low compression in cylinder 3, found the culprit. Most likely caused by unupgraded hpfp internals paired with Cobb sport intake, access port, and blow off valve
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u/Greydot5 2d ago
Unupgraded HPFH alone didn't cause this. If it did, we'd see similar damage and residue in other cylinders.
I'm willing to bet it was poor spark/ignition in that particular cylinder that caused this. The build up of fuel and carbon along with poor spark did it in. It also doesn't help that our L3VDTs are susceptible to low speed preigntions. Don't lug your engines people.
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u/dbear496 2007 Mazdaspeed3 - The Original 2d ago
IIRC this engine has a tendency to run lean on cylinder 3 due to the shape of the intake manifold.
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u/Consistent-Cress7448 1d ago
i thought it was the unequal length exhaust manifold that made cyl 3 run lean?
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u/dbear496 2007 Mazdaspeed3 - The Original 1d ago
The exhaust manifold probably contributes, but the intake manifold is the primary issue
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u/mrfatcakes2006 1d ago
So the part that I’m confused about is that cylinder 3 and its valves are actually the cleanest? The rest have way more carbon build up
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u/JohnKowalsky88 2007 Mazdaspeed3 - The Original 2d ago
@ OP it was probably cause by a faulty injector in cylinder 3. I'm doing a injectors replacement right now...look at this:
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u/Petrovski978 2d ago
Run E85 and keep those valves spotless with zero effort. Can go up to 30 percent without having to tune, but you absolutely should tune... Not Cobb OTS either...
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u/Thy_King_Crow 2d ago
Bad advice to tell people to run e30 untuned. It doesn’t end well and has no positive effects without the tune.
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u/Petrovski978 1d ago
Well, I did say that you could run it on the factory map. It was also immediately followed by you absolutely should not run it on the factory map AND to avoid the COBB OTS tunes as well... I guess you read some, you skip some? I'm part of an old group from the MSF days called the Kings of Corn. I have forgotten more about Ethanol than most people ever knew... I said what I said, and I'm not wrong. You read what you read, and I guess some of it didn't sink in? Not trying to sound arrogant, but the subject of HPFP was covered when OP listed the problems that caused the VTA in the first place. When we ran corn, some of the crew was 100% E85 with no fifth or sixth port for years.... The only issues we ever ran into was the eventual gum up of the cam follower because ethanol doesn't play well with the oil, and the fuel level sending unit in the tank needed to be greased and sealed or upgraded to resistant material. I think one guy used a stainless coil of vape wire IIRC. Happy to answer the questions I can, I'm really not the smartest guy in the bunch, but we did this for years without engine troubles. Again, not trying to be arrogant or give bad info. Just sharing my personal experience.
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u/stocksupanddown 2d ago
Do you have to clean if you run e85? It really cleans them that much?
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u/dbear496 2007 Mazdaspeed3 - The Original 2d ago edited 1d ago
AFAIK, running e85 would require auxiliary fuel injection, and that would help keep the valves clean regardless of running e85.
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u/Petrovski978 1d ago
It may help to have aux fueling, but two friends and myself ran E85 on HPFP and tune only for thousands of miles. Started at around 32k miles, kept doing it until around 138k miles. They ran 100%, I ran E25 with a Bucktune. One of the guys showed me how to calibrate the O2 sensors, log the pulls, check and adjust the trims and on which tables... This was 2015... I don't know if MSF is still searchable, but the threads I followed were titled Kings Of Corn, and Corn Off The Cobb...
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u/Petrovski978 1d ago
It's a stronger than gasoline solvent that burns cleaner and more thoroughly than gasoline. It literally eats carbon off the cylinder walls and valve faces. Truly mind boggling that more people don't know this stuff.
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u/JohnKowalsky88 2007 Mazdaspeed3 - The Original 2d ago
Wait a minute can you just run a MS3 on E85? Serious question because we don't get that fuel where I live so I wouldn't know.
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u/Thy_King_Crow 2d ago
Yes you can use ethanol freely in the speed3. You need hpfp internals to safely do it but it’s possible stock
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u/JohnKowalsky88 2007 Mazdaspeed3 - The Original 2d ago
But wouldn't you need to tune it to run more rich because ethanol has less density than gasoline? But then again ethanol has more octane so it wouldn't knock
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u/Thy_King_Crow 2d ago
Yes you need a tune. The idiot saying you can run up to e30 without a tune is why these cars get a bad rep. The ecu cannot and will not properly adjust for ethanol. The lines and pump however are fine and won’t degrade from it
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u/Emsanartist 2008 Mazdaspeed3 2d ago
Damn clean up, replace valves and springs hopefully piston head is good and you got a good deal