Turbo bog from standstill

[Svante]

Apex -06 with a rear mounted gt2860RS and RB3 unit w, 3bar mapsensor and oem baro connected to the pressurepipe. I run a 0,079" headshim with stock internals. Sleds runs and pulls great but sometimes when i WOT it from standstill in deep snow it just lands on it´s face. The first that struck my mind was lack of fuel. But my Wb lambda ( brand new ) keeps telling me i´m in the low 10´s when the problem occurs. Boost is 12lbs on stock fuel pump and injectors. Can the WB lambda tell me wrong numbers because of the bog? When trail riding in low/high speeds and then WOT the problem seems to be gone. First i thought the air filter froze up, but the problem is still there after installing a filter sock ( KN pre-filter ).

Any ideas that can help me solve the problem would be great..

Running premium gas at sea level. The sled hits rev limiter sometimes because i´m trying out some different weight setups, but i don´t think that would cause this problem.

thanks
/Svante

 

[mbarryracing]

Svante,
I had a slight bog when quickly wicked WOT from idle, too. Never really solved it but got around it with a higher idle (1800 RPM) and a higher engagement 4K+.
Does your do it when hot?

Why is your bar sensor in the pressure pipe? Try just hanging it in atmospheric, the RB3 is what should be adding fuel to match rising boost pressure alone, not the stock ECU.

 

[Svante]

Svante,
I had a slight bog when quickly wicked WOT from idle, too. Never really solved it but got around it with a higher idle (1800 RPM) and a higher engagement 4K+.
Does your do it when hot?

Yes, or i always drive it softly til it reaches stable temperature. It really falls on the nose when it happens, like you shut it down. One time i almost fell over the damn thing LOL. I tried the TORS bypass but it did´nt help either.

Why is your bar sensor in the pressure pipe? Try just hanging it in atmospheric, the RB3 is what should be adding fuel to match rising boost pressure alone, not the stock ECU.

The reason i connected the stock baro to pressure was because of a post i read about the rb3 having trouble of adjusting in higher altitudes and the problem was solved by doing this mod. I do some different altitudes riding so i made the mod right away. Do you think this would be an issue?

Thanks for the reply.
/Svante.

 

[mbarryracing]

OK, I didn't know about that RB3 issue, but that resolution doesn't make sense to me and I think its bunk...
The OEM bar sensor is the same sensor type as the OEM MAP sensor. Lower elevation has more air pressure and gives a higher reading so the ECU add fuel %(richer), higher elevtion is less air pressure and hence less fuel % (leaner) and it's not a big difference in Kpa pressure compared to intake pressure (boost).
Putting it in the charge tube exposes it to positive air pressure and maxes it out hence givin you a richer AFR. The problem is if your running 12 lbs boost in the tube then the sensor still sees 12 lbs regardless of elevation. 12 lbs is 12 lbs, the sensor can't differentiate altitude...
What it is doing is giving you richer AFR at idle, that you don't want, because the turbo is spinning and pushing air at idle which creates a slight Kpa difference, enough to fool the ECU that it's at a lower elevation and adds fuel (richer).
I'd take it out and hang it...

 

[Svante]

OK, I didn't know about that RB3 issue, but that resolution doesn't make sense to me and I think its bunk...
The OEM bar sensor is the same sensor type as the OEM MAP sensor. Lower elevation has more air pressure and gives a higher reading so the ECU add fuel %(richer), higher elevtion is less air pressure and hence less fuel % (leaner) and it's not a big difference in Kpa pressure compared to intake pressure (boost).
Putting it in the charge tube exposes it to positive air pressure and maxes it out hence givin you a richer AFR. The problem is if your running 12 lbs boost in the tube then the sensor still sees 12 lbs regardless of elevation. 12 lbs is 12 lbs, the sensor can't differentiate altitude...
What it is doing is giving you richer AFR at idle, that you don't want, because the turbo is spinning and pushing air at idle which creates a slight Kpa difference, enough to fool the ECU that it's at a lower elevation and adds fuel (richer).
I'd take it out and hang it...

I see your point. I was just happy about a fix for the RB3 elevation problems and jumped on it right away i found the post if you like to read it: http://www.ty4stroke.com/viewtopic.php? ... +elevation

On the other hand, i don´t think this would be the issue. If the oem baro would give me problems the sled would bog every time i reach 12 psi. But i have only experienced it on WOT from standstill in deep snow. Could´nt just be a boost spike due to the increased restriction that causes it? Still don´t explain my low AFR reading though

The boost controller is a AEM Tru-Boost and i dont know what the accuracy is on that one.

/Svante

 

[mbarryracing]

No, I wasn't thinking that was the total cause of your bogging but you never know because it's a variable that no one else is doing.
I was just thinking it wasn't really doing anything for you and might even be hurting performance by not providing any altitude comp at all...
Logically once you are above a slight pressure in the charge tube, the BARO sensor goes above the range that the ECU uses anyhow. If it's typically below 100 Kpa for ambient air pressure, at 2 psi boost (115 Kpa) it no longer doing anything for you (stops adding fuel...) so I don't see how putting the BARO sensor in the charge tube helps the RB3 do anything different at different altitudes because it seeing the same pressure under any boost (pegged out).

But then again, maybe they were just on the cusp of not being rich enough at WOT so that added what they needed...

OK, you need to clarify your bogging issue, I was under the impression this was happening off idle but your post above leads that it's happening at 12 psi boost WOT? Two different scenario's...

Are you sure it's not clutching that is causing your bogging?
Is your intercooler happen to be heat soaked when this happens?

 

[Svante]

Sorry for my writing :/

I will try to disconnect the baro hose and se how it runs.

The boost is set for 12psi. At the trail in low or high speeds it pulls fine. The only time i´ve experienced the bog it when giving it full throttle in deep snow from standing still and when the boost arrives. Not at the exact moment i hit full throttle.

But either way the boost is still 12psi. Maybe a small spike but it´s hard to tell.

Hope the explanation was better than the last one . English it not my main language.

/Svante.

 

[mbarryracing]

It's highly likely that could be actually clutching and not the engine at all. Sounds like the secondary is shifting out under that particular load and pulling the engine down.
In deep snow my RPM's use to actually surge up and down 1K+ RPM at WOT because of my trail clutching shifting and then backshifting under the changing loads, it was just like a bog... thought it was fueling and it was very misleading because it was perfect on the trail or track... but take it off into the deep and darn it...

 

[Svante]

I believe you´re right.. I drove for a while today and made another deep snow pull when i came back just to be sure i did´nt misread the wb lamda. And the clutch belt burned up :/.. The secondary must have shifted quite a bit.

So i think i will aim for higher speeds out in the deep before i WOT it in the future


Thanks for the inputs.

/Svante.