Engine/Transmission (1994 - 1998) so lets talk 12v

[Mhannink]

well the other day i did a little performance tunning on a guys truck. everything went perfect no problems and i dialed it in where he wanted it on the first shot. was pretty stoked about seting it all once and not having to tune it anymore. anyways back to the subject at hand. wich is this thread really has no one subject i just want to talk 12v. my idea for this was i have been thinking of all the little things you can do to gain a little extra power. things like adjusting the afc, removing the afc spring, different fuel plates, the rack plug, etc. i know a fair amount of these things but thought a thread with all these things in there would be good able to awnser any ones ?s on what how where when why. so lets talk 12v

 

[MAllen]

well, that's pretty open ended. Sounds like everything in this 12 valve forum could come after that post.

 

[Forrest Nearing]

removing the AFC spring isn't "tuning"

 

[pwerwagn]

removing the AFC spring isn't "tuning"

LOL!!!

Mhannink, are you thinking something along the lines of the sticky thread on the 1st gen forum, all the steps for bombing a VE mota??

If so, that would be a cool thread to have around, and would save lots of redundant questions. however, the search feature also does the same.

--Jeff

 

[Forrest Nearing]

it is nice to have it all in one place... sometimes the search function can be frustrating when you want to look up terms with only 2 or 3 letters

 

[Mhannink]

well this stems from me being bored and just wanting to talk trucks yes it is open ended because this thread has no set topic just I TRIED TO BY-PASS THE CUSSING FILTER chat.



i know the search feature can be frustrating i have used it. i suppose this is along those same lines as the first gen forum though i didnt know it was there.



i know a fair amount of tricks to do to a 12v but i doubt i know them all. things like drilling the fitting to the afc housing out to allow faster throttle response is one that comes to mind. like i said in the begging lets talk 12v and if a moderater sees this fit to be a sticky then i think it would be good

 

[Joseph Donnelly]

geez, and I used the stiffest afc spring to make 800 hp

 

[WDixon27]

yea really, just last night i got totally pizzed off trying to find a thread about 6. 5 chevys and gave up after 5-10 minutes, what was really annoying besides the 15 second wait but when just trying to search for "6. 5" wouldn't work, for some reason typing "6. 5 chevy turbo diesel" still gave me the not enough words error #@$%!

sometimes the search function can be frustrating when you want to look up terms with only 2 or 3 letters

 

[Vaughn MacKenzie]

Well let's get this thread on track for MHannick. How about we discuss AFC springs and what ones are available and when it would be appropriate to change out the stock one. This is a subject I haven't explored much.



How many different springs are available, and from who? Joe Donnelly implies the higher you go in HP the stiffer spring you would want. Makes sense because if you're running high boost pressures and want fuel somewhat linear over the PSI range then you'd want a stiffer one to resist the heaviest fueling 'til you're coming to a full boil, right?



With different spring rates and the ability to preload them with the star wheel you certainly have a few combinations to play with.

 

[Forrest Nearing]

the bigger injectors you've got, the more AFC spring you'll want

 

[JWashburn]

On my '97 it seems I drive using the first say 1/4 of the go pedal travel. A stiffer AFC spring might make more of that travel useful?

 

[Jim Fulmer]

The AFC or aneroid is a wonderful tool if you know how it works and use it to your advantage, it's really nothing more than a communication tool for the pump, when do you want it to fuel and how much.



People that remove the AFC arm or take a plate out of the pump do so because of lack of patients and or knowledge, if this was such a good idea guys like Joe D. and myself would be or would have done it.



The AFC spring (stock 215) is what I call a 40lb spring; a 180 pump spring is what I call a 20lb spring. There are times when a 20lb spring will work better and time when a 40lb will work better and both can be increased or decreased with the star wheel that do nothing more than add or subtract tension.



The first tool to have is a hand held air pressure regulator, without it everything is just a guess and it does nothing more than simulate boost.



Jim

 

[JFaughn]

Pictures , don't forget pictures , & a thousand words , did I forget to mention pictures ?
Then also the whys & why nots , understanding helps to make decisions .
I'm fighting hard to not add more power till I upgrade the trans.

 

[Hammer]

IMO...

The absolute first step in "tuning" any 12v is for the owner to baseline what he has to start with... . Some of these could be included...

-Fresh service and filters.

-New belt if needed.

-Check and/or adjust the valves.

-Make sure the exhaust manifold gaskets are not pushed out or compromised.

-Check fuel pressure to ensure the proper pressure is had.

-Make sure the wastegate is not frozen up(see that alot on older rides).

-Make sure radiator is clean and not hampering airflow.

-Make sure the charge air cooler has no leaks.

-Check throttle cable for wear and make sure its allowing full throttle.



Once you have gotten a good service baseline then you may want to add some after gauges to monitor EGT's and Boost at least. Then before you change anything you should find a local dyno and at least baseline as stock so you know what you have and what each change will do for you. I keep records of each part installed on my truck and what its benefits were. good or bad.



You then will need to decide on what you goals are,buy your parts accordingly and B. O. M. B. on till your heart desires... ... . Andy



On Edit...

One thing I forgot to add is this... There are many "free" types of modifications out there,some work and some are just dangerous. When it comes to those type of modification be wary of what you do and spend alot of time researching them before doing something you may end up regretting later.

 

[Mhannink]

Well let's get this thread on track for MHannick. How about we discuss AFC springs and what ones are available and when it would be appropriate to change out the stock one. This is a subject I haven't explored much.



How many different springs are available, and from who? Joe Donnelly implies the higher you go in HP the stiffer spring you would want. Makes sense because if you're running high boost pressures and want fuel somewhat linear over the PSI range then you'd want a stiffer one to resist the heaviest fueling 'til you're coming to a full boil, right?



With different spring rates and the ability to preload them with the star wheel you certainly have a few combinations to play with.

see this is what i was looking for i didnt even know there where heavier springs available. or that as i see later on different pumps had different springs.



so can anyone tell us who offers these other spring options?



as for tunning it i personaly have not had a truck with high enough boost to make a stiffer spring worth while (plus my buddies and i are all real young so we want lots of smoke). we always loosen them or remove them completely again for smoke.



from reading all this though it seems like there is a lot more to the afc and its affect on power then i thought. so a higher spring rate set a little loose will fuel hard enough for smoke but not full fuel correct? then as boost builds smoke clears afc moves clear and the gov arm rides on the plate fully fueling the engine(at least as the plate shape and settings are concerned).

 

[Forrest Nearing]

it's not high boost pressure that makes you need a stiff spring... it's big injectors



think about it... boost covers fuel. the stock AFC is set for a certain amount of rack travel per psi... bigger injectors = more fuel at a given track travel

 

[Mhannink]

ok this again is all for smoke control right?

 

[MrDiesel]

LOL!!!

Mhannink, are you thinking something along the lines of the sticky thread on the 1st gen forum, all the steps for bombing a VE mota??

If so, that would be a cool thread to have around, and would save lots of redundant questions. however, the search feature also does the same.

--Jeff

This is the best idea I've seen here yet! Some one get it started!!! Moderators?

 

[Vaughn MacKenzie]

ok this again is all for smoke control right?

Yes, and EGT control too. With bigger injectors you reach full fuel at boost levels too low to handle it, the spring is fully compressed (allowing full fuel) at say 25lbs boost. Add a stiffer AFC spring and full fuel is delayed until a higher boost level is achieved, say 35-40lbs boost.

 

[Hammer]

Mhannink...

Another way to expalin it for you,maybe this will make it easier...



Softer AFC Spring=Earlier fueling and Earlier Power curve.

Stiffer AFC Spring=Later Fueling and a later Power curve.



By changing the AFC spring,softer or stiffer,you can also determine how much torque your truck will make. The sooner it goes into full rack travel and full fueling,the sooner the power is made,thus elevating the torque number.



Stiffening the spring moves the combo higher up in the rpm band and will lower the torque number. The higher rpm at which it goes into full travel and full fueling the less torque that will be made.



It depends on how you want to drive your truck where or what spring you use. Some guys like the low end snap and use the soft spring and some like the top end and use the stiff spring. Only you know how you wish to drive and its something you need to play with to see what you like. The gentleman who did my pump chatted with me for hours on how I drive,then did the pump on the stand and nailed it perfectly and I have not changed it at all.



As for smoke control,the only true way to limit it,is moderation of the right foot. How many of us can really do that,LOL... ... . Andy