Thread: Running MSD injectors at 4 Bar?

I have heard some talk about not running MSD injectors at 4 bar, why is this?

not sure, but i know for a fact they will not run correctly at all

ive ran my msd 72lbs at 4bar at no problems, however realisticly for powerwise my 72lbs at 3 bar are more than sufficent for what i want. so i just went back to 3bar

it really depends on the size of the injectors, as to weather or not you really need to run 4bar. youy might see better fuel automization,better fuel burn, better gas mileage, with 4bar, but if your injectors are nig enough to suffice the power you need, i would just stay at 3bar

It has to do with the coil strength of the injector. The msd's were not meant to run any higher of a base pressure than 3 bar as any higher of a base can cause the injector pintle not to open due to the lack of coil strength in the injector. This could cause serious problems if for some reason the fuel pressure over powers the coil strength and you injector all of a sudden under boost when fuel pressure goes even higher based on boost levels and doesnt open, then guess what, Lean.

Most of the ID injectors can be set to up to 100psi base pressures without problems. While they have tested other injectors that supposedly could handle 100psi base pressure and saw capsizing of the injector when fuel pressure went a bit higher.

I have 50lb injectors now and I am thinking of running E85 and don't want to switch injectors at this point. I don't think I want to take the risk of running into issues at WOT and running lean.

Now how do the the top feeds differ from side feeds as far as make up of the inside of the injectors. Sorry for the questions, I am trying to educate myself on this matter.

what all are you upgrading to run the e85?

Just take a look at the two, haha. The coil inside our sidefeeds is for one bigger than the msd injectors but that is not the main contributing factor. Its all in design. They have a spring that keeps the pintle tightly closed. Then there is just the design of the coil inside to open it and how its set up.

Our sidefeeds and most aftermarket sidefeeds are perfectly fine to run at 4 bar and maybe even higher but i dont think higher pressures have been tested that much on them either. The ID injectors are actually thinner than the MSD's but just have tons and tons of R&D into them that makes them a great topfeed injector that can run insanely high base pressures without running into problems.

Its just the fact the MSD's were not made to run at 4bar and when you run them at the higher pressure they may not perform exactly how they are supposed. Leave them at 3bar and upgrade your injectors to 75lbs or something. With E85 your going to need alot more fuel than just bumping the fuel pressure up.

i also agree 50lb injectors are probably not going to cut it you are going to need 72lbs to 1000cc injectors maybe llarger depending on your goals what managwment are you going with

All I know is that Im one of those people who said **** what everybody else says Im gonna try it. With the SAFC you can tune a 3 bar ECU to 4 bar. I ran them at 4 bar and they didnt stay closed. They ran Static and STUCK OPEN at WOT. You could watch the A/F's go rich.

Ashton Ive never heard about them staying closed. They go static and stay OPEN which make the motor bend a rod or something else because it cant compress the floeded cylinder.

You have to watch for this on Big High impedance injs also. Like for instance, from my research people were blowing motors trying to run RC750cc's at higher then 3 bar because they would run static. I researched all of that because I was gonna run 4 bar on my 750's. But apparently its not recomended. Just step up to some 72lbers. You can find them cheap. THen if your on a budget get an SAFC to tune them until you can get the setup you want.