I recently got my setup professionally tuned. I was running a turboxs mbc and we started with the boost controller off running wastegate pressure ~9-10psi, then upped the boost until we got to 14-15psi falling to 12-13. It made good power and the air fuels looked good..,

I recently decided I wanted to try it with less boost so I can see if 1st and 2nd can hook up on my new M&H DOTs. I took the boost controller off and now in 1st and 2nd gear it bogs like crazy and the air fuel ratio is a lot leaner under WOT like 13.5-14.5:1 on my wideband (I got out of out the two or three times I saw it get this lean). I was wondering if taking off the boost controller has effected the tune that much or is the load way higher now in those two gear since it doesn't spin?

I haven't tried any higher gear as I fear it would be bad with the higher load.

 

it could be a bit of both...

normally if your setup was properly tuned at a higher boost level and you lower the boost level it should still run fine.

while technically the load on the motor has increased due to a traction increase your afr shouldn't be that high, of course this goes back to the properly tuned part.

if your tuner didn't do any part throttle, part load tuning across the rpm range or do any street tuning after the dyno session to get the high/medium load cells cleaned up across the rpm range (think a 4th gear pull from say, 50mph or any light throttle input in higher gears) then it's very possible that it's all in the tune.

do you have the ability to take a screenshot of your fuel and ignition maps? if you could provide those along with the rpm/load range this is happening at we could better help you in determining the cause/issue.

 

thanks for the input...

1.he did tune part throttle/tip-in and idle as well as WOT.

2. I can't take any screen shots as I don't have crome or any program currently. (he tuned it with Crome Pro)

3. 1 more variable I forgot to mention was that I noticed the top to the jdm gsr throttle body port was open to the atmosphere and I wan't sure if it blow off or what but I capped it at the same time I took out the boost controller.

thanks again guys. I'm trying to figure this out while I'm at work. haha

 

Sounds like when you took the controller off you may have introduced a boost/vac leak.

 

I figured it might be. I've learned its always the last thing you've changed that always is the problem so I figure its either a leak somewhere because of the boost controller or vacuum cap on the throttle. Is it ok to cap the top part of the throttle body?

 

What top port? do you mean where the OEM map sensor was?

if that was open then you had a vacuum/boost leak during tuning. if you capped it afterwards that could very well be causing your issues. it doesn't take a huge leak to cause an AFR problem.

put the boost controller back on with that port capped and see what it does. if it runs leaner than before you know it was a leak.

 

Boost controllers generally help spool the turbo, since the WG/spring-only will tend to open prematurely ever so slightly. My guess is the tuner only tuned the boost columns he hit, not the boost levels below wastegate pressure. A good tuner will do at least some of the vacuum columns, then take a guess at the low boost columns he can't reach by interpolating between the tuned vacuum and boost columns.

 

^^^this...

I was thinking it might be something like this since the mbc being taken off or a possible vacuum leak were the only two things that changed. It has to be the tune or my fuel system all the sudden took a ****. I put the boost controller back on exactly how it was (didn't cut vacuum line or move adjustment know)so I'll hopefully update soon. I live in Florida so of course its been raining all afternoon/evening.

 

Yea this is what I was trying to explain lol. If he didn't tune any of the low boost and vacuum columns that the motor didn't hit during tuning it could be causing your issues

 

Took it out again...and it seems like it's doing the same thing still!

One new thing to report, now that I think back I don't really remember if my air fuels have been good since according to the guage since the tune/switch to e85. I got it tuned and only did a couple pulls in 3rd and wasn't really paying attention to what the AEM guage was saying. It cruises in the mid high 16's:1 (gas afr) which seems a little lean but I figured since it's low load and e85 it should be fine.it seems to chug along with no problems.


Do you think the AEM uego sensor might be just off or going bad? I think the tuner did say something about it reading a little lean in comparison to the tailpipe sniffer (which I always though read lean anyways) but 2.5:1 off seems like a lot. When he tuned it the air fuel curve was a straight line just under 12:1 afr.

Or could it be a sudden fuel problem? From what I can tell the injectors, fuel pump, sensor and pretty much the complete build was done back in 07. I bought it recently and rebuilt the motor and turbo.

 

one other dumb thing I fogot to mention or think about. When I got it tuned it still had ~2-3 gallons of 93 octane in the tank. I know E85 requires more fuel so maybe this is the problem now that I've gone through another full tank of e85.

 

Think it's resolved. note for anyone make sure you have ZERO 93 octane when you get tuned. I drove it around for a while tonight and filled it up with almost 3 gallons of 93 and it's seems to be doing a lot better. When I originally took it to get tuned I just drove it around for ~200mi thinking it would almost empty the tank and ended up filling it with 8.5 gallons of e85 thinking it was a less than 10gallon tank.