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Discussion Starter · #1 ·
i left a thread on here this weekend about resetting my computer and it making a hell of a difference... i spiked at 19 pounds of boost and held 17... the car was running like a raped ape... all with the apg wastegate hooked to the factory vacuum line... no line tricks done as of yet.... but now it has been a few days and the weather has dropped to around 50 degrees at night... this morning i get it let it warm up and i let it rip and only hit 17 psi.... and held like 14.... from my understand the stage one pcm does not control the boost at all as compared to the stocker.... so would it my wastegate being hooked up to the stock line cause this much flucuation in boost???? I am trying to elimate this hit and miss with the amount of boost i pull.... would a boost controller solve this problem???.... when i tried the vaccuum line lottery last weekend i had no luck anywhere i never got it to boost over 10... Can someone please help this could cost me a race one day and i am trying hard to figure this out and get it fixed....
thank you
 

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I think your computer is still controlling boost.... i could be wrong though... but im pretty sure if you hook it up to the factory line it will control your boost after it has learned it.... i would recommend hooking it up the the green,blue, or TB if you dont want the computer to control your boost...
 

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Discussion Starter · #3 ·
ok here is where i starting turning dumb.... when i did hook it up to those lines last time the turbo wouldnt boost past 10 with the wastegate tightened way up... am i doing something wrong....i tried every possible line lottery on here... and 10 was the best... i just cant stand not knowing how much boost my car will pull from day to day
 

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d_fl8ted1 said:
from my understand the stage one pcm does not control the boost at all as compared to the stocker
Where did you get that idea? I'd always been under the belief that ALL the SRT-4 ECU regulates boost to put out a set amount of tourque over the rpm range. This is why cool weather you get less boost, because the cool air makes more power.
 

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Discussion Starter · #5 ·
oki am starting to understand now... the cooler the air the less the car needs to boost to make the same power... am i correct on this... as far as the pcm controlling boost i may be confused on that but it seems i have read some where that it didnt but like i said i could be wrong... i am just thinking i need a boost controller to solve this problem
 

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d_fl8ted1 said:
i just cant stand not knowing how much boost my car will pull from day to day
Perhaps go for an N/A car, their boost is quite predictable.

Seriously, when you start playing with the boost control on this car you are in for some tuning.
 

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The srt4's PCM is a "boost controller" and a fine electronic one at that. The stage 1-3 PCM will increase boost (often dramatically) compared to stock. The PCM also boosts based on throttle position/rpm/gear and puts the right boost at the right time. For example boosting 17-18 in first gear with the PCM bypassed for example is insane IMHO.

I tried every arrangement and concluded the stock line run to the wga (adjusted to hold 15psi) with the pcm driving solenoid #2 as intended was the fastest and safest best performing method of them all.

I just don't understand why people insist on bypassing the best electronic boost controller made for the SRT4....... the PCM itself.

They may think its faster or stronger, but I challenge them to back it up with 1/4 mile results compared to a Mopar designed standard stage1/2 hookup.

Give the PCM some love :thumbsup:
 

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Discussion Starter · #8 ·
ok romans i get you.. you have helped me much in the past.. so your saying leave it where it is and just build on other areas of the car to help performance... so one more question for you romans would you put a electronic boost controller or any type of boost controller for that reason on our cars
 

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d_fl8ted1 said:
ok romans i get you.. you have helped me much in the past.. so your saying leave it where it is and just build on other areas of the car to help performance... so one more question for you romans would you put a electronic boost controller or any type of boost controller for that reason on our cars
obviously its just my opinion........ and I don't want to discourage others from doing what they see fit for their cars, but "high boost" and aftermarket boost control is only part of the overall situation. Real power gains are comming from fuel management and bigger turbos.

If I still had my SRT4 I would be saving up for the Mopar stage 3 kit, I believe it will deliver solid, dependable, well engineered safe power. More importantly it will be usable and drivable for the long haul. With my stage one car I got 17psi (and higher spikes) with 15 to redline day in and day out (all summer) with just a FM (Garrett) wga set up with one turn of pre-load. it work and ran very very well. Coupled with a 3" dp, Borla catback, and K&N intake the car was very quick and very reliable.
 

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I tried my APG wastegate with the PCM boost controller. After the fisrts test, I had to reduce the arm's tension to minimum since I was getting 19-20PSI !!!!

Please don't run it at 19 PSI with only stage 1... you will run lean and burn you pistons very quick....

We tried it on my friends SRT-4 and got 1600F at the manifold!!!! We had to reduce the boost or it would have turned very bad for his engine....

Now I have the Greddy Profec-B and I like it better since I decide where I want the boost to be now... There is even a boost limiter to make sure you don't overboost, you have to admit that we are not always looking at the boost gauge when pushing it hehehe.

Be carefull with the PCM boost controller as it boost a lot more in 4th and 5th gear!!! Luckily my friend was there to look at the gauge!

I was running around 16-17PSI in 2nd and 3rd gear but 19-20 PSI in the higher gears!!!!! Very bad!
 

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slamcool said:
Please don't run it at 19 PSI with only stage 1... you will run lean and burn you pistons very quick....

...

We tried it on my friends SRT-4 and got 1600F at the manifold!!!! We had to reduce the boost or it would have turned very bad for his engine....

...

I was running around 16-17PSI in 2nd and 3rd gear but 19-20 PSI in the higher gears!!!!! Very bad!
Sorry, but this is absolutely wrong. I posted a couple threads on Stage 1's maximum performance a month back. I've been running 20-21 psi on Stage 1 for a while now, with an A/F ratio of 11.8:1. Also, EGTs are steady at ~1450 degrees while cruising and slightly above ~1600 degrees when WOT for extended periods of time. Just to show that isn't bad, I've also done tests running Stage 1 in its intended pressure zones (under PCM control). Granted, the A/F ratios are pig rich (the S1 injectors flow enough fuel to run pig rich until about 18 psi), the EGTs still remain steady at ~1450 degrees while cruising and slightly above ~1600 degrees when WOT. And yes, those EGTs are from the exhaust manifold.

So it is entirely possible to run higher boost levels on Stage 1 injectors than allowed by the PCM; however, boost control becomes very bad when the PCM is taken out of the pressure loop. Therefore, your BEST method would be a DSABC (Dual-Stage Automatic Boost Controller), which I am currently installing on my car now. Allowing your PCM to control the lower boost levels, and then routing control of the higher boost levels to your MBC or EBC allows your turbo to spool up and down as intended while still allowing you higher end power.
 

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Discussion Starter · #12 ·
ok rydiak.. it seems tha tyou know what you are talking about so with my mods... i need a dual stage controller from turbo xs to control my boost and remain safe...i have never worked with a dual stage but i am sure i can figure it out... would you recommend that one or even a electronic boost controller... money is no object... i would really like to boost 20 and hold at around 18 so lead me on my way....
 

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Discussion Starter · #14 ·
ok i read that entire post...still confused on how the whole setup works... i understand the reasoning but i mean wouldnt a dual stage boost controller do the same justice
 

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No, since the PCM would have no control over lower boost with a normal DSBC. The whole PURPOSE of this setup is giving the PCM control over the lower boost.
 

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Well Rydiak, I guess we are saying the same thing, I did not specify WOT sorry about that. I always have 1/4 mile races in mind... Keeping it at 1600F and above is really not good!!! It's dangerous, plus, you will certainly knock on pump gas, that's what I want to clarify, if you race few hours like that... hummm.

For my part, I won't do it for sure...

For the ~1450 degrees, I dont get it... I mean while cruising, you dont get 19PSI do you?

For the injectors, I know we are fine, some of my friends are running in the low 12 with their 550cc on DSM cars, so I'm sure we can do good stuff with that, our are similar. I'm more afraid of the PCM behaviour at that level of boost. I prefer to get an SAFC or e-manage with a data logger to see what's going on in there.

Are you getting knock at all? Did you get some log? I'm really interseted in knowing more about what's really going on in there.

For now, I'll still keep it around 17-18 PSI, I just wanna be on the safe side before I get more info...

And for the DSABC, that sounds really interesting. You think it can do better than the Profec E01 ?
 

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No, you don't get 19 PSI while cruising. Usually between -10 Vac and 5 PSI. It is the engine RPMs that generate the ~1450 degree exhaust temps though, not the pressure, so boost levels have no impact at cruising speeds (zero acceleration). You will notice that our cars run stoichimetric at 14.7:1 while cruising and idling, hence why differentiating boost pressures have no impact.

http://srtforums.com/forums/showpost.php?p=1068394&postcount=22

And I am a huge fan of the DSABC setup because it keeps the PCM in the pressure loop while still allowing you to increase your maximum boost pressure. I'm not sure if the E01 can do that..
 
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