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Originally Posted by Eric_Oz_S2
Besides ending up with wonky afr's, the other problem with a "mechanical" tuning approach is you can't adjust timing. Rrfprs go hand in hand with mechanical distributors. And believe me, you want to be able to retard the ignition on these engines to get both performance and safety. If you log knock with standard timing and say 7psi boost, you will see that the dme (s2, 968 and turbo) pull a lot of timing. Without knock control you will end up with detonation.
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Hi Eric - Have you done this before? No argument that boost related timing pull is desired at a certain level and you would want to watch detonations. On the other hand, if you tune the rrfpr and intercool correctly then more aggressive timing can work to your benefit... Above a certain level you would want to control the spark as well.
Quote:
Originally Posted by Eric_Oz_S2
What also happens with higher ful pressure is you affect the injector spray pattern. Go to high and you loose power as the injectors stream instead of spray.
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Injectors do have a limit to pressure published. The finer mist cone injectors (Siemens DEKA for example) don't like high pressure but the squirt injectors respond quite well. The squirt style injectors are designed to impact the intake valve with the fuel spray as a method of atomization and the cross benefit of cooling/cleaning the valve. I've used fuel systems with squirt style operate around 130PSI for burst operation... the system ran for years after first assembly in 2003 and I still drive the engine today but on MS2Extra. No failures, multiple races... ran like a clock, dead reliable.
Quote:
Originally Posted by Eric_Oz_S2
Another problem is that rrfprs are mechanical devices that tend to vary pressure over time as the rrfpr wears.
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That's a bit of a stretch... everything on cars wears out but that doesn't mean we don't use them. Spark plugs, Piston rings, valve guides etc all slowly wear. Fuel injectors cycle too many times and lock. I think if you want to deter the use of the device then you should explain the strain on the fuel pump and accelerated wear leading to a shorter life. That is a potential side effect that you may experience after several years and hundreds of thousands of miles of use. Parts do wear out...
Quote:
Originally Posted by Eric_Oz_S2
No argument that they are a "cheap" solution (assuming you don't factor in possible engine damage), but arguably they are not value for money given the abundance of used injectors on the market and cheap tuning tools.
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I don't disagree but I did point out that I've seen far, far more damage from programmable EFI users messing up their tune and exactly NONE from a RRFPR properly tuned - I'm only saying there's more than one way to skin a cat. There's a whole other set of lessons that are in practice that have been finely honed and through the tumbler for decades. To deny that these options exist or do work well.. then as the saying goes, "Ignorance is Bliss." I'm not saying everyone should tear out their programmable systems - I'm just saying there's another way to do it that works very well and is more economical.