Detroit 12.7 Injector Choice??

Don't worry about the number of holes. The tips are sized A1-A6, B1-B6, etc. Up to E5...there's no E6. The higher the letter/number combination, the higher the flow.

 

The way i understand it is this.
The older ddec 2 and some 3 had 8 hole.
As the epa emissions progressed detroit went to 9 hole . They did this to atomize the fuel better to keep the epa happy. The holes are smaller on the 9 hole but they manage to keep flow numbers up because of the extra hole.
In general the 8 hole injector is a dirtyier injector so to speak.

I took my 7635 9 hole out of my 14l ddec 4 and installed 5915 with 8 hole.
Noticeably more smoke on shifts.

 

So did 5915 work out better for you than 7635? Any negatives besides more smoke on shifts? Improvements?

 

Well heres the deal.
The 5915 i got were remans but they dont seem to run right. Im getting issues with engine hunting, surging and running ruff when not under load. Im going to send the injectors back for Warrenty and put my 7535 back in.

Under load the 5915s seem to run ok. 2-3 psi more boost and it will smoke more on shifts but so far not a big diffrence over the 7535s i had..

 

It seems to me that when you change/upgrade injectors and/or mess with ecm, proper mechanical tuneup is crucial. I did my out-of-frame but reused my older injectors for they tested OK; we flashed ecm for custom tune, etc, and some time later I started having some weird issues that appeared to be mechanical injector-related. So changed a whole pack last year. A different mechanic put them in and tuned up. Ecm settings didn't change. And on the first run noticed about 25% loss of pulling power. Went back to the first mechanic to re-tune. Turned out that the second guy used Detroit factory tuneup numbers for my serial (injector height, etc), and originally my engine was rated for low hp. So after that "correct" tuneup, power came back.

But bunch of other problems remained. Fuel asphalting - bad, nasty stuff, also blowby was getting worse, etc. Right now replacing the entire fuel system. Dropped the tanks and had them steamed out. Installed FASS. Replaced all the fuel lines for expensive ones that are rated for everything, and fittings. Hooked up that magnetic fuel conditioner (not sure if it would help any, but found one cheap so why not.) At some point down the road plan to install a fuel cooler to complete the setup and will surely use fuel stabilizers at every fill-up.

Also injectors. My serial calls for 7466. I'll try to go with 5915. General consensus here is that they perform well, also seem to be similar to my stock (7466 - B5; 5915 - B6) so would give a higher flow. Just have to make sure mechanical tuneup is done right.

Anyways, fingers crossed. 2 weeks in garage already, Will see. But what is a better time than this? February, spot rates are as low as ever....

 

The higher letter/number, the higher the flow seems straightforward. But 5915 is B6, and 7650 is D1, so 7650 should be a step-up for a flow? But folks here claim 5915 flows better in comparison. A little confused here. Please elaborate. Thanks

 

You got to set your injector hights to what cam shaft you have. Not what injector.
Its the lift on your cam shaft inj lobe that dictates what to set your inj hight too.

Not sure what your Mecanic was doing but you can do lot damage on rockers and rollers if you set them wrong.

Mine are all set correctly, i just got a bad set of injectors that were not built properly. Live and learn right.

 

good info, swaan. Thanks. Yep live and learn

 

My 12.7 has 5915's with a bw 171702 turbo bully dog manifold air dog champ 2 and a leon tune and my truck will run hard and egts stay in check. Next for me is a 4912 cam and she will really get up and run.

I can home from indio ca friday evening grossed out around 65k nothing crazy but i was able to run up the hill coming out of there at 55-60 mph loaded and egts never got over 800.

 

Does a 4912 cam work well with 5915's? My serial calls for a 1681 cam. Which one is better, you think? Both seem similar, just different inj heights.