Don't hate - I'm trying to do some tuning on my own right now. I have the Vortech Si trim with 3.33, which means I will probably hit 10 psi. I took it out for some street tuning last night and hit 4 psi, and things look good (rich though, but a good start, no knock). I have yet to go WOT though, since I don't want boost to spike in upwards of 10 psi w/o having gone through 5 psi, 6, 7, etc.

So, my question is: If I set the boost cutoff on the UTEC to 5, go WOT until cutoff, then 6, do the same, and continue up to 8 psi (don't want to go any higher right now) - is that safe for the motor? The fuel cutoff is very abrupt (not like a rev limiter), so I'm a little nervous that doing so isn't the best for the motor. However, since boost builds fast, I don't know any other way to go WOT w/o hitting peak boost.

I think once my houses sells I'm going to get a carputer so I can keep an eye on things at all times (and get meth/water injection)

Thanks guys. Once I get the motivation I'll post up a build thread along with all of this tuning stuff.

- Jon

 

i didnt even know that function worked. sounds like a poor way to tune though.

Having seen the TN base map and maps that 2 different tuners have built for me, they arent that much different, in the fact you could get a redline pull safetly.

 

interupting a motors performance will be hard on the motor, fuel cools the engine down in a combustion...

 

Yup, the function works.

I'm sure with the map I have I could boost up most of the way. I just wanted to kind of go a safer route, but if this is too harsh, then I can just do one hard pull and adjust from there.

^ when there's no combustion, there's nothing to cool. It only happens for a split second anyways.

 

That is why you first load a base map since base map are really conservative to begin with. If you are using UTI then just set you Audible to sound as soon as you hear 1 knock. As soon as you hear a beep then let go of the gas... The danger is continuing while you are knocking.

 

Alright, cool. I was doing that anyway (audible alert), so I'll just forgot the fuel cutoff (except at 8 lbs +). If it does knock, I'll totally feel the timing fall on its face as well and back off.

Thanks guys - I'm sure there will be more questions to come

 

How much timing do you remove for every knock? The good thing about utec is it will do it for you automatically so you are still safe.

 

I dont think the fuel cut can be set that low anyway.

It is scary when it hits.

 

I actually have to look at what timing it pulls when in open loop (timing map). I think it's at the stock setting which pulls up to 5 degrees?? Can't remember, and can't remember what the step is either.

But now that I think of it, it really won't fall flat on it's face. It fell flat on it's face when I had a knock count going back into 0% load and ECU timing took over, since the settings for that pull a ton more timing than what it does when you have a timing value set in the cell instead of ECU. As for the knock, it happened a few times when going from 10% to 0% and the ECU timing kicked in (still good AFR) - I think this happened because I had my TPS threshold at 20% and it registered going below the TPS threshold before it went from boost (10% column) to vacuum (0% column). I changed TPS threshold to 0 now, so it will always be in open loop whenever I'm in boost.

Oh, and I'm running the TN base timing map, which seems to be very conservative.

 

It works when it's that low, but it ends up going about 1 psi over the threshold. I would assume boost is still building in the intake manifold, since the throttle isn't closed. Hmm...thinking about it now, it seems like the bypass valve wouldn't open due to no vacuum yet, if you kept on the throttle boost would still be created (but not increased - or would it?), and the injectors would kick back in once you fell under the threshold. I'm almost thinking you could have a scary overboost situation immediately after the fuel cut - although I always think things through completely wrong.

Either way, it's pretty darn scary when you hit it...and it will be even worse if I hit it at 8 psi.

 

Jonny, are you are running the TN base fuel map for 550cc injectors? If so be aware that the map will be VERY rich with 650's. I used the same basemap and have the same injectors (although I have a TN ST). I am about 3000 miles away from my car so I can't check for you, but I believe my 0 load column up to like 2000rpm is scaled to -18 or -19, something in that range, on my 8psi tune (which was done by a professional tuner, not me).

 

This happened to my car. I did an exahust mod after i had it tuned and it boosted more psi. The car feels like it hit a brick wall when it cuts boost. My car still drives just fine tho.

BTW, i had it retuned. Runs great now.

 

Thanks Spoils - I'm running a modified fule map that was used previously with this kit (same blower, injectors, etc.). It is way rich right now because it was run 2 to 16 psi instead of 0 to 10 psi for me, but I'm working on that. I went with the TN timing map though because the previous owner had aggressive timing on a built motor.

I'm trying to get the fuel map down, but JT is probably coming up to WI next month so I'll probably have him do the timing for me.

 

Im in the same process......waiting till spring to get a good tune.
Trying not to run it too hard on the base tune.....but when sorting out my boost controller....hit 17 psi :-( nothing happened , but the car felt really good :-)
My base tune is set for 8 psi , but with hitting above that I deceded to keep the psi at 10. It has been there for a couple months now but I did hit the cut off , was a little freaked out.....dam chick in a mustang was harassing me....but I put her in her place and blew by her when it happened , pulled over cause I was a little worried.....got her number....lol
Anyways....im running TN ST with a built engine , car is being put away in a week for the winter , and getting new clutch flywheel and upgrading fuel rail system with a return line.
Should my pro tune and return line on the upgraded fuel rail sort out that cut off?

 

Probably bad for the drivetrain/ motor mounts than anything else. Yea, it's abrupt. I set it pretty high (12psi on a 9psi tune) since I only want it to kick in if there's a real problem.

 

your engine fuel cuts every time you let off the gas and coast down RPM. there is no harm in it. If anything, like djamps said, it could in theory beat up your mounts or drivetrain by cutting at high load and RPM, but thats probably stretching it

 

except cutting the fuel for overboost protection is cutting it during load..... fuel cut under load is always a no no. decel cuts fuel but is also the lowest possible load on the engine.

just asking for bad things to happen since a majority of combustion chamber cooling comes from fuel as well. might be good 10000 times but theres always that chance of something bad happening, if its fuel cut it needs to be 100% from that cylinder and hope theres no residual trying to ignite off.

 

No is not a no no. It's perfectly fine. Just like when you let off the gas at high load. You worry too much.

 

when you let off the gas at high load though its no longer high load, the throttle plate shuts, vacuum jumps and the engine is now under no load/very light load where it is unlikely to detonate anyway. what your saying denys the existence of detonation from under fueling which does for a fact happen.

your comparing literally apples to giraffes and trying to associate two events that are nothing alike. as i said the only way at all that fuel cut is even remotely safe is if that injector turned off 100%, which is why the race logic units completely turn off injectors at random to cut power.

what your promoting is going full throttle and then just randomly reducing injector duty cycle while still under power, nothing like letting off the throttle at high load thus resulting in cutting fuel at no load/low load. the ecu dosnt jump to low load cells when you let off the throttle because it enjoys to, the engine is no longer at high load.

 

I am well aware of everything that is occurring. There is no load when injection is shut off, no matter what the throttles are doing.

It seems that you are not understanding what fuel cut is. Fuel cut means the injection has been completely shut off. There is no detonation because there is nothing to detonate. Your engine becomes an air pump that is only spinning because the drivetrain is engaged. There is no combustion to cool or detonate. No fuel was injected.

Do you also worry about your air compressor detonating?