Front vs Rear rotor EGT..
 

For high boost applications (25psi), on average, how much % fuel do you guys find you're adding to the rear rotor to equalize your egts. I am adding as much as 6-7% to my rear staged injector on my haltech to have my EGT's come within 50* of each other, with the rear still being the higher. Does this see normal? Do you guys find yourself adding this much fuel?

Thanks for your replys

are you on the stock LIM? Why not go with the xcessive equal length? I don't know about your specific question just curious. I'm going with the xcessive manifold when I go single.

Still on the stock LIM.

Just trying to rule out any other problems such as blocked injector. If other folks are running as much as 6% more to the rear rotor, then I think I am ok. Just dont know if others are running that much.

i used to find on my old s5 intake setup used to have about 50degc different at idle but as load came on and especially into boost would be nearly identical.within 5degc of each other normally.sensors were identical placement of each other approx 20mm from manifold flange.(i realise you have a fd so results may vary)

i don't really know, but i do have two thoughts.

the first is that if you add 6% to the rear, you need to make sure it doesn't run out of duty cycle. for instance if you're running 85% injector duty, and then add 6% to the rear, the rear might be at 91%, which is kind of high. i'm not sure how the ecu will display that...

second, the EGT's on each rotor depend on a few different things (intake we know about, but exhaust manifold might matter, coolant temp front vs rear etc), and i wouldn't expect them to be the same, so if the correction is under say 10%, i'd think its fine.

the third thought is if you had flow numbers for the injectors to put the one that flowed the most in the rear, but that's a bit obvious

Another issue that causes uneven fueling is uneven heating of the LIM from turbo heat.

What kind of heat shielding are you running?

Did the best I could on shielding, wraped downpipe, turbo blanket, shielding plate between LIM and Turbo.

Just got through switching the probes from F to R to see if its actually the EGT guages causing the difference.

My personal experience with front and rear EGT probes is that they are very sensitive to location.

Before you look too much into adding fuel to try to get the numbers the same, without knowing anything at all about your setup, it may be more likely that a temperature discrepancy will be as a result of probe placement.

Both the proximity of the probe to the exhaust port and the depth of the probe in the exhaust flow are critical to getting comparable temps.

Arran

Tempwise, what your seeing is typical for my ride as well (about 30C difference with rear housing running the warmest). I'm running Ground X LIM with Power FC, so no ability to enrich just rear injectors only.

My EGT probes are in identical positions in respect to distance from exhaust ports and depth.

Switching the probes made no difference in EGT's Rear rotor still runs about 50*F than the Front rotor. I suppose that 50* difference is acceptable, but the ecu still has 6% more fuel added to the rear secondary injector.

what exhaust manifold are you using?

^^Custom SS 2" short runner.

Stock lower has shorter runners to the rear rotor, so it tends to run leaner/hotter with all other things being equal. Exhaust manifold design can also affect your egts. You said your probes are in identical locations. What about the runners? Are they equal length?

Front Runner is shorter.