4.5 injectors in a 4.2 manifold?
Discussion
I have just modified a 4.2 manifold to go on my 4.5. The original injectors in the 4.2 manifold are Bosch 280 150 744 and have a long reach spray guide but are not the correct size for the 4.5.
My original 4.5 injectors are the Lucas D1720CE but do not have the extended metal spray guide fitted ......is it OK to use these in the 4.2 manifold or will i need to get same 4.5 injectors with the extended spray guide.
My original 4.5 injectors are the Lucas D1720CE but do not have the extended metal spray guide fitted ......is it OK to use these in the 4.2 manifold or will i need to get same 4.5 injectors with the extended spray guide.
Not sure tbh, the original 4.2's are rated to flow 235cc @ 3 bar, I think the Cerb runs at 3.5bar and the 4.5 Lucas types are I think rated at 310cc. When you do the sums both of these types are supposed to be marginal for the power but in practice they 'work'.
I run replacement 4 hole red top bosch which are rated at 325cc (945's I think, but be careful not all red tops seem to be the latest 4 hole type).
Not sure if that helps directly with the question but hope it helps in some way.
I run replacement 4 hole red top bosch which are rated at 325cc (945's I think, but be careful not all red tops seem to be the latest 4 hole type).
Not sure if that helps directly with the question but hope it helps in some way.
The overall fuel gain setting in the MBE 4.2 ECU is less than the 4.5.
I'm certainly no expert but I seem to remember reading somewhere that overall fuel gain is used to change the fueling characteristics to match changes in flow rate caused by changes in fuel pressure or different injectors. Possibly why it was getting too much fuel through the 4.2 injectors?
I'm certainly no expert but I seem to remember reading somewhere that overall fuel gain is used to change the fueling characteristics to match changes in flow rate caused by changes in fuel pressure or different injectors. Possibly why it was getting too much fuel through the 4.2 injectors?
JonnyW said:
We tried this on the racing Cerb with flowed and ported 4.2 heads and apart from flames that were like the Batmobile it overfuelled to a degree that you got pi%%%d on the vapour!! Needs a serious remap, if possible!!!! with this swap over!!
Found this too, the characteristics are so far way from normal AJP the remapping of the MBE is extensive and not restricted to the usual trimming. I understand even my reference points were changed. However once the MBE is cracked then the results can be had. The last head flowing and mapping left it at 460+ but impossible to hold on the rolling road for any length of time to get it spot on so my lump is being pulled again in the new year to be put on a bench dyno to see what it really can make in better controlled conditions
. Jonnyw what size butterflys did you manage to get in them 
, as you may know I scrapped a couple of sets trying to get around the corner.
just a thought if you have a set of flowed, ported and bigger butterfly 4.2 intakes sitting around I might like to try them on the bench dyno, my existing ones are flowed but standard sized butterfly and still make the power, be intersting to see if there's any more to be had and allow the 'bigger butterfly is best' be put to bed ............ or not.
, as you may know I scrapped a couple of sets trying to get around the corner. just a thought if you have a set of flowed, ported and bigger butterfly 4.2 intakes sitting around I might like to try them on the bench dyno, my existing ones are flowed but standard sized butterfly and still make the power, be intersting to see if there's any more to be had and allow the 'bigger butterfly is best' be put to bed ............ or not.going back to my original question do you have to use injectors with the extended sray guide in a 4.2 manifold or is it OK to use the standard lucas style injector without the spray guide.?
Harry I got 48mm butterflys into the 4.2 manifold. Standard is 45mm. The problem comes slightly past the butterfly where it starts to bend if you try and open this out to 48mm then you break thru the topside.
I flowed mine and broke thru on 1 of the 8 inlets. Howerever I did not scrap the unit I had the hole pluged and welded and dressed it up afterwards.
Harry I got 48mm butterflys into the 4.2 manifold. Standard is 45mm. The problem comes slightly past the butterfly where it starts to bend if you try and open this out to 48mm then you break thru the topside.
I flowed mine and broke thru on 1 of the 8 inlets. Howerever I did not scrap the unit I had the hole pluged and welded and dressed it up afterwards.
HarryW said:
Jonnyw what size butterflys did you manage to get in them , as you may know I scrapped a couple of sets trying to get around the corner.
just a thought if you have a set of flowed, ported and bigger butterfly 4.2 intakes sitting around I might like to try them on the bench dyno, my existing ones are flowed but standard sized butterfly and still make the power, be intersting to see if there's any more to be had and allow the 'bigger butterfly is best' be put to bed ............ or not.
Harry, we (well Andy is!) are building two engines to compare perforamnce, one is based on a more standard format of 4.7 using the same rods etc..the other is a full on lightweight race engine, Carrillos, Cams etc... We are going to run both in the Cerb but also with the more standard engine we are going to try two heads 4.2 ported and 4.5 ported and different injectors. The only way to see what is best is to run and run on a consitent circuit for a weekend, which will probably be the GT Cup exclusive test days at Snetterton in March. Set up will be on a rolling road prior to this. Cheers Jonny, as you may know I scrapped a couple of sets trying to get around the corner. just a thought if you have a set of flowed, ported and bigger butterfly 4.2 intakes sitting around I might like to try them on the bench dyno, my existing ones are flowed but standard sized butterfly and still make the power, be intersting to see if there's any more to be had and allow the 'bigger butterfly is best' be put to bed ............ or not.Gassing Station | Cerbera | Top of Page | What's New | My Stuff