I reciently tunned my intake cam gear on the dyno, and we ended up with giving it 5 deg of advance. (Exhaust is still at 0) It made about 10hp more, but there's one issue after tunning.
If I'm crusing on the hwy at say 70, 80, 90mph (light load) and I let off the pedal, my EGT's will climb 100 - 150F.
Example. At 80mph cruse, the car runs at 1450F, I'll take my foot off the gas, and the EGT's climb to 1600, for 1 sec, then go down to 1200, 1100, 1000....

Could it be that i'm pumping Exhaust gas back into the manifold now with the extra overlap?

Any help is appriciated.

 

Oh, the car is an 01 prelude (H22)

JRSC @ 9psi
Hondata S200b
Kami Header
2.5" exhaust

 

cam timing can affect EGT's for sure........

but also you may be dumping fuel when you let off the throttle causing EGT to slightly climb before dropping back down.....

is your hondata s200 fully tuned?

 

ya, the S200 is fully tunned,

Actully, when we moved to +5 int cam setting we only added a bit of fuel everything else is the same. I'd say the A/F was about .3 leaner at +5 than at 0. SO like i said we only added a bit of fuel. Could I be dumping fuel even after I let off? and does hondata have a way to change this?

 

The momentary enrichening is a normal function of letting off the throttle. If you have a wideband, you'll see it hit 12:1 to 13:1 just after letting off and then a slow return to expected AFR's.

 

I just think it's strange that it never did this before... I know Hondata does not have control over this function, right?