HELP! Blew engine, and am now paranoid. Need help/opinions.
#61
This is on the MSM IHI Rh55 turbo. A true piece of ****.
So why is everyone saying his stock injectors can't handle 8psi?
OP, Why didn't you just use a NA base map to tune for boost? Worked for my MSM motor on 99 base map.
#64
That's why. All of the discussion on NB injectors is interesting but irrelevant to OPs dilemna.
OP, bottom line on the science is this:
You have a barrier between two chambers. The chambers contain fluids at different pressures. If you make a hole in the barrier, fluid will flow from the chamber with higher pressure into the chamber with lower pressure. How much fluid flows depends upon two things:
1. The pressure difference between the chambers; and
2. The size of the hole.
So, if you need more fuel, you've got a choice: increase the pressure difference, increase the size of the hole or both. Doing nothing burns pistons as you inevitably go lean.
For most of us that use MS, increasing the size of the hole is the most expedient answer and leaves the rest of the system per Mazda design (including materials, resistance to leaks, etc.). The injectors you mentioned (ID725s) will work beautifully for your application.
OP, bottom line on the science is this:
You have a barrier between two chambers. The chambers contain fluids at different pressures. If you make a hole in the barrier, fluid will flow from the chamber with higher pressure into the chamber with lower pressure. How much fluid flows depends upon two things:
1. The pressure difference between the chambers; and
2. The size of the hole.
So, if you need more fuel, you've got a choice: increase the pressure difference, increase the size of the hole or both. Doing nothing burns pistons as you inevitably go lean.
For most of us that use MS, increasing the size of the hole is the most expedient answer and leaves the rest of the system per Mazda design (including materials, resistance to leaks, etc.). The injectors you mentioned (ID725s) will work beautifully for your application.
#65
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This was in response to someone who had said "The NB runs higher fuel pressure than the NA."
Well, yes, sort of. But not by much, and the NB's fuel pressure does not rise as MAP rises, so at moderate levels of boost, the NA is actually quite close to the NB in terms of fuel pressure (and will exceed it after a certain point.)
#66
I never stated what size the NB's stock injectors were, just gave an example of how any one specific injector would perform in the two different fuel systems (MAP-references vs. static.)
This was in response to someone who had said "The NB runs higher fuel pressure than the NA."
Well, yes, sort of. But not by much, and the NB's fuel pressure does not rise as MAP rises, so at moderate levels of boost, the NA is actually quite close to the NB in terms of fuel pressure (and will exceed it after a certain point.)
This was in response to someone who had said "The NB runs higher fuel pressure than the NA."
Well, yes, sort of. But not by much, and the NB's fuel pressure does not rise as MAP rises, so at moderate levels of boost, the NA is actually quite close to the NB in terms of fuel pressure (and will exceed it after a certain point.)
if his fuel pressure also raises and eventually surpasses an NBs it effectively raises the size on the injector as well.
If the stock injectors are very small I can understand why it blew because of fuel. but right now I'm just understanding aggressive timing.
I'm just trying to understand this further, sorry for inconvenience.
#71
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Remember all cells are interpolated in between each other, so the 'lack of resolution' isn't technically correct, there's a lack of breakpoints, but not resolution.
#72
Actually, you need more in lower KPA regions. That's where you do all your part throttle driving, above 100kpa, you're generally at WOT, don't have large changes in VE and therefore don't need many breakpoints at that point in the table.
Remember all cells are interpolated in between each other, so the 'lack of resolution' isn't technically correct, there's a lack of breakpoints, but not resolution.
Remember all cells are interpolated in between each other, so the 'lack of resolution' isn't technically correct, there's a lack of breakpoints, but not resolution.
#73
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I just think he may have tip-in issues or issues climbing hills when targeting 15-15.5:1 between 2000-3000 RPM. That's a little too early to go THAT lean. I'd bring that back to 14.7 and reserve the 15s for cruise areas only, like above 3500.
#75
sorta pointless, you dont need the resolution there and that table is pretty good.
I just think he may have tip-in issues or issues climbing hills when targeting 15-15.5:1 between 2000-3000 RPM. That's a little too early to go THAT lean. I'd bring that back to 14.7 and reserve the 15s for cruise areas only, like above 3500.
I just think he may have tip-in issues or issues climbing hills when targeting 15-15.5:1 between 2000-3000 RPM. That's a little too early to go THAT lean. I'd bring that back to 14.7 and reserve the 15s for cruise areas only, like above 3500.
with that in mind, what about these as break points
KPa = 20, 28, 40, 57, 81, 115, 164, 230
rpm = 700, 1000, 1400, 1900, 2600, 3600, 5000, 6800
In a generic sense, are there certain "events" at which you want to align your KPa or rpm breakpoints?
Any guidelines on percent change between?
Last edited by mx594m; 06-25-2013 at 12:34 PM. Reason: additional questions
#79
Its mostly personal preference, but certain rpm and kpa breakpoints are definitely helpful.
IMO:
You want at least one row in high vacuum, 10-20kpa
You want as many rows in the part throttle and cruise areas because that's where you'll be most of the time
You want at least one row over your target kpa in case you overshoot target
You want 1 rpm row lower than your idle target, 1 at target, and 1 slightly over
You want to stagger them evenly in the midrange/cruise
You want 1 rpm row at or a little past your redline/fuel cut
That's how I try to set mine up anyways
IMO:
You want at least one row in high vacuum, 10-20kpa
You want as many rows in the part throttle and cruise areas because that's where you'll be most of the time
You want at least one row over your target kpa in case you overshoot target
You want 1 rpm row lower than your idle target, 1 at target, and 1 slightly over
You want to stagger them evenly in the midrange/cruise
You want 1 rpm row at or a little past your redline/fuel cut
That's how I try to set mine up anyways