2095 (Mack) rack plug on a 215 pump

Had a 2095 rack plug laying around as I was about to throw my 215 pump back on for an event coming up since the 13mm is still acting up. Remembered reading mixed reviews about it a while ago so I looked again and couldn’t find a straight answer, I did a little experimenting with my pump on the bench to see for myself.

In all the pictures below the afc and plate are removed and the throttle lever is tied to WOT.

First image you can get an idea of the maximum rack travel with the stock rack plug. In the second image you can see that port closure will happen on the slant of the upper helix where the start of injection is delayed since the plunger must raise further to close the spill port and start the injection process.

For the last images I installed the 2095 rack plug. In the third picture you can see that there’s more rack travel as shown by the return spring being compressed further. With this extra rack travel you can see that the plunger is now rotated so that port closure will happen on the flat top of the plunger which essentially advances the start of injection at max rack travel compared to the stock rack plug.

From my little experiment I can’t see a reason to not run the 2095 rack plug on a 215 pump. Can anybody see something I’m missing? Maybe there’s more to it? Any input would be appreciated. Just killing time and trying to learn something while I get my 13mm problems figured out.

Pump from manual or auto? - Competition Diesel.Com - Bringing The BEST Together

Read through this. Essentially what you have found is correct.

It was one of my biggest upgrades with the 215 pump after all the rest.

215 pump has timing advance at idle and once it travels the extra about the Mack rack plug allows the timing will start to retard .. kinda don't help extra fuel less timing

Rich dzl said:

215 pump has timing advance at idle and once it travels the extra about the Mack rack plug allows the timing will start to retard .. kinda don't help extra fuel less timing

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According to Seth, this is not true.

1stgensleeper said:

Pump from manual or auto? - Competition Diesel.Com - Bringing The BEST Together

Read through this. Essentially what you have found is correct.

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Thanks, that's exactly what I was looking for, I must've missed that one. What confuses me a little is where Seth says the pump will only reach 14mm of rack travel in factory form but the stock rack plug allows for 19.5mm of rack travel. Is he saying that the factory fuel plate limits rack travel to 14mm and it'll go to 19.5mm with no plate? Could something else hinder rack travel?

Plate and afc is all that can limit travel. I've ran a rack plug in a 160 pump, a 180 pump, and last a 215 before I went to a 13mm. In my case the rack plug was a gain with all, but made the biggest improvement with the 215. The 215 was also the strongest running pump I've ever ran, even over a 180 pump with the exact gov springs and rack plug.

A person might want to keep in mind, depending on what timing you are running, that the pump will give more advance at higher rack travels. So if you are pushing the limit on timing I would back it off a few degrees. On the test stand port closure is set at 12 mm rack travel, which is in the retard notch. Both lower and higher rack travels will offer more advance due to the shape of the notch. That being said, the rack plug will allow your pump to flow 600+ cc. And they run great.

Another point that was brought to my attention is the fact that the lower helix and upper helix are essentially running away from each other at higher rack travel, so while the effective timing may be increasing so is duration which isn’t exactly ideal. That also kind of explains why 215 pumps like nitrous.

Got the truck back on the road with the 2095 rack plug in the 215 pump, timing was set to 20* at the top of the plunger. The turbo seems to come up really well but at wot the truck just pukes smoke and boost is down a little, if I lift off the pedal a bit the smoke clears and boost comes back up. Makes perfect sense with the increase in duration, hoping I can fix that by giving the truck more time to burn it with more timing. Gonna set base timing to 24* today which should make for around 30* at full rack travel.

zachu812 said:

Got the truck back on the road with the 2095 rack plug in the 215 pump, timing was set to 20* at the top of the plunger. The turbo seems to come up really well but at wot the truck just pukes smoke and boost is down a little, if I lift off the pedal a bit the smoke clears and boost comes back up. Makes perfect sense with the increase in duration, hoping I can fix that by giving the truck more time to burn it with more timing. Gonna set base timing to 24* today which should make for around 30* at full rack travel.

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Is this the truck in your sig but with the 215 pump? Sounds like you are overfueling it on the top end if its puking smoke at WOT.

zachu812 said:

Got the truck back on the road with the 2095 rack plug in the 215 pump, timing was set to 20* at the top of the plunger. The turbo seems to come up really well but at wot the truck just pukes smoke and boost is down a little, if I lift off the pedal a bit the smoke clears and boost comes back up. Makes perfect sense with the increase in duration, hoping I can fix that by giving the truck more time to burn it with more timing. Gonna set base timing to 24* today which should make for around 30* at full rack travel.

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That's the exact same thing that happened with my 180 pump. I went from 21deg to 23deg and it's pretty perfect to ~3300 rpm. If it gets smokey past that, I don't care much because I rarely do it anymore...

At 23deg it's a little tough, but I can start my truck at -25F without plugging it in.

I don't think it's exactly over fueled, it seems that there is too much duration with my injector/pump combo so that the end of injection is too late to take advantage of all the fuel.

Last night I bumped timing to 24* and went for a drive with similar results but it seemed a little better, I then made the jump to 30* with no change other than I can't stage the truck from a stop. I'm going to drop timing back to 20* and either put a fuel plate back in or swap DVs to effectively cut the duration back down.

On a 215 pump with a rack plug, it is possible for the rack to rotate the plungers past the lower helix cutout and get to where the 12mm pump flows 800+ cc's of late, sloppy, and un-usable fuel. If Seth chimes in, I'm sure he can give duration numbers and flow numbers but I'll bet the injection window goes from the typical 28 to 32* range at normal max injection using the lower helix to 50 or more degrees of duration..... and you aren't going to successfully run 50* advance to hopefully burn it so you end up with a bunch of late unusable fuel that drops boost and creates a smokey wet mess.

Yep, what he said. That's kinda what I was getting at in my post above. I've had my best luck using a plate or AFC controller on the 215 pumps. If you get past the lower helix you are essentially injecting fuel for the stroke of the cam minus pre-stroke (port closure) lift height. Been a while since I measured degrees of duration, but yeah it's way too much.

Has anyone measured the distance from the bottom of the lower helix to the top of the plunger on a 180 and compared that to the same measurement on a 215 pump? With all this extra duration it seems to me that distance would have to be greater on a 215 pump to explain the longer duration.

Still for some reason everybody seems to eat up these 215 pumps like it’s the hottest thing short of a 13mm and I just can’t figure out why. Guys have made them run with good results, maybe a more mild DV will decrease duration enough to take advantage of the timing advance? The extra fuel goes out the window with that idea but you might actually be able to take advantage of the earlier port closure with the upper helix.