Mercedes injector Nozzels with shimmed injectors & d8a

[bayley]

speaking to a bloke on tdocuk forum and he was saying to get some Mercedes injector Nozzels with shimmed injectors and a d8abottom end....anyone heard of this being done ?
he also replyed with this.....qoute Standard bosch injector cracking off pressure is 175 bar if you fit Mercedes injector Nozzels the pressure changes from 175 too 260 or even higher so you have them calibrated so there all equal but you need the 11 mm metering head as the 9 will struggle with the pressure.

[strictly_perv]

Interesting.
.....Waits for Ruan/Darren/Dave to reply.

[dturbopeck]

I know the derv doctor updated injectors use merc nozzles, I even had a part no for them, but that's gone now,

[swampy]

Find the merc part number and I will see what price I can get them for

[Dan!]

I set some injectors to 190 bar I think for zx_volcane to try out but he hasn't said anything about effects/differences yet. Worth noting aswel that higher break pressures will slightly retarded the timing so you will want more static advance to counter it.

[zx_volcane]

Ahh yes, never did comment on that

Can't see/notice any real world gains from higher break pressure, might be a tad louder, might also help a tad with the bio diesel i run, but all could be in my head. Would be nice to think I'm getting more fuel in the same duration.

I did nudge the static slightly to compensate, and I'm running an 11mm head.

Thing is my injectors were so knackered that just having new nozzles was a dramatic improvement, I had crazy hesitation at certain rpms/loads which has now cleared.

i also strapped on the gt25 at the same time - which doesn't help tie down any performance increases.

[Ruan]

I've heard from a few sources that the Merc IDI nozzles aren't a perfect match for the Comet V precups our engines use... People have used them and have found the precups crack quicker... Remember that Mercedes used their own design precups, so I wouldnt be surprised if they specified their own design... Bosch don't release any of the OEM specifications which is why its so difficult half the time..

There's other nozzles which are more suited IMHO... Although injector nozzles on IDI engines are not really as important... 200+Hp has been made on OEM nozzles at OEM pressures...

[CJ_Derv]

I've heard from a few sources that the Merc IDI nozzles aren't a perfect match for the Comet V precups our engines use... People have used them and have found the precups crack quicker... Remember that Mercedes used their own design precups, so I wouldnt be surprised if they specified their own design... Bosch don't release any of the OEM specifications which is why its so difficult half the time..

There's other nozzles which are more suited IMHO... Although injector nozzles on IDI engines are not really as important... 200+Hp has been made on OEM nozzles at OEM pressures...

Would i be correct in saying DVS' would be a better modification rather than nozzles

[bayley]

i will try and get a bit more info of him about them.

[darrenjlobb]

I know where theres a set of highly chronic 220bar IDI injectors, all fitted / ready to go in an XUD, cant think where though just waiting for someone to offer the right money for them Brand new near enough!

The break pressure isnt going to make a deal of difference on the XUD tbh, in theory the higher it is, provided your pump can still flow the same fuel at that pressure, should be a tad better, but you wont notice it in the real world, The reason you crank up the pressure is if you run CHRONIC nozzles, as otherwise if they pop off at normal pressure, you get nothing more than a squirt of diesel rather than a nice mist, so I normally crank the pressure up to allow it to still mist, and flow alot more fuel....its VERY crititcal in DI as the injectors are so sensitive...but on the old IDI, is makes much less difference, what it can do though, is allow your advance system on your pump to carry on working much closer to a stock curve, even with LOTS more fuel, as line pressure / plunger stress remains fairly low, so timing can still work as normal

[cwspellowe]

I've heard from a few sources that the Merc IDI nozzles aren't a perfect match for the Comet V precups our engines use... People have used them and have found the precups crack quicker... Remember that Mercedes used their own design precups, so I wouldnt be surprised if they specified their own design... Bosch don't release any of the OEM specifications which is why its so difficult half the time..

There's other nozzles which are more suited IMHO... Although injector nozzles on IDI engines are not really as important... 200+Hp has been made on OEM nozzles at OEM pressures...

Would i be correct in saying DVS' would be a better modification rather than nozzles

Not necessarily, as if you modified/used different DV's you could end up with a crap load more fuel in the lines, the pressure would build earlier but the injectors would then break earlier too. You wouldn't necessarily just get more fuel, you'd find the injectors break too early too.

Higher flowing DV's in my head would work well with higher break nozzles though, as you'd have more chance of breaking the nozzles at the same time as standard ones if the pump's flow isn't up to it.

[Dave]

You don't want ridiculous pressures into your lines, they will only expand more, as the stock injectors cant let the fuel out quick enough. IDI's like long continual burning durations, thats what gives them their epic torque compared to petrols which is all bang and done in one shot/similar to DI. Having the pumps release all the fuel in one shot is counter-productive.