Low boost?????

[Jack in Alaska]

I recently installed Bosch 275 RV injectors. Got them from my son JR2. He got some larger ones so I got his leftovers. They make a considerable difference in the pulling/acceleration power with out any increase in egt's.

My problem is... the boost on my truck used to be in the 20 to 21 range when stock. The boost has degraded to 17 max. The new injectors had no effect on that. I pinched off the rubber hose from the turbo to the the wastegate. After hitting 2nd gear and punching the pedal the boost went up rapidly to 22 and climbing telling me the turbo is fine.

What is the problem and how can I fix it?



(I took the vise grips off of the rubber hose after that little experiment. )

 

[R.ebel]

Leaks

Jack in Alaska, Sounds like you have a leak. Check your all of the clamps between the turbo and the intake manifold.

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[Jack in Alaska]

Rebel,

I checked the clamps several times. Also... . how would it spool up to 22 with the wastegate bypassed if the hoses were leaking? I am not trying to be argumentive but what you suggested does not make any sense with the problem I have.

Thanks for the info anyway.

I am wondering if there is an adjustment on the wastegate that would delay the pressure dumping back up to 21 +/-.

 

[TXRam]

Jack, contrary to what some say, you need a boost module with a modified elbow for the turbo. When I put the 275's in without these, I could only make 18-19psi. After boost module and elbow, I got 28psi - and MORE power and LOWER EGT's.



Like the previous post says check your intercooler hose connections - if you pinched the hose with the 275's, you should make quite a bit more than 22psi more like 26-28psi, and then you should feel the ECM cutting fuel since you don't seem to have a boost module.

 

[JR2]

Okay here is the deal, Jack in Alaska's (here after refered to as Dad) truck used to see 20-21 psi when driving with the stock injectors in. He has 80K miles on the truck and he has seen the boost drop off over the course of the last year. His truck now only makes 17 psi boost at WOT. He has checked the hose connections and they are all tight. We he pinched off the wastegate hose he hit 21 psi in third gear and backed off to prevent an overboost code. This to me indicates a few things. First is that the hoses from the turbo to intake are all fine and the second is that the MAP sensor is fine and not causeing defueling of the truck. I think the problem is that the wastegate has become misadjusted some how. When Dad took it to the dealer last he asked them to check the boost and they said it was "in spec" but who know what that means. Has anyone else seen this sort of thing?? Do wastegates get out of adjustment?? I am fairly sure I can adjust the wastegate myself, all I have to do is loosen the nut and then turn the rod to shorten it??



We put in the 275 injectors to give him some more power and for fun, we may just get him a boost module and elbow, but I really don't think it is necessary for just 275's.

 

[Steve Campbell]

I read somewhere on this forum that it only took something like1/10,000 play in the waste gate to give the performance results that you are describing. Check that and either add an extra spring(external) or shorten the linkage to eliminate the play(if that proves to be the problem). Hope that helps!

 

[TXRam]

John,



Yes, the spring in the wastegate actuator could be getting weak. There is a "pin" in the rod you're talking about - you'll have to drill it out to adjust the rod. Or you can shim the rod side of the actuator where it's attached to the turbo (effectively shortening the rod).



I posted the following on another thread (I agree the elbow and module is not necessary, but it definitely helps power and EGT):



"This has been said many times, but I disagree that you don't need an elbow and boost module with the addition of mild injectors or boxes. This is based on tests that I and another member conducted - here is a description of each and the results: Installed 275HP injectors in a 99 2500 QC 4X4 5-speed 3. 54. 1500-3000rpm tests were done to compare results. Totally stock times averaged 12. 7 seconds (3 or 4 trials per average - I can't remember which). 275's only - times average 11. 7 seconds (a 1 second improvement). 275's w/ elbow and "Redneck" boost module - 10. 5 seconds (another 1. 2 second improvement). Definite improvement even with the mildest of HP upgrades - as a matter of fact, more improvement with the addition of the 275's and elbow/boost module, than the 275's by themselves!



Now I agree that all the boost you can get (which is what most elbows give you) is sometimes too much, but an increase in air is needed with EVERY increase in fueling. "

 

[Jack in Alaska]

An update on the low boost problem..... My son, JR2, took out the map sensor for a cleanup job. it was ok. He also took out my SPA boost gauge to fix, for the umpteenth time, the poor connection.

He discovered that the brass reducer fitting in the engine had stripped it's threads. This probably caused a leak of pressure. He replaced the reducer with a steel one, taped the threads and now I can get 19psi boost.

The 275 injectors are a real improvement on power.

I will probably be installing a boost module and elbow soon.

My intention is not significant bombing but to increase the power to tow a 5th. whl.

Anyone figuire out how to fix the SPA electrical connection at the boost sensor? It is a real "hoaky" setup and prone to failure.