During the dyno testing yesterday we had some fascinating lessons on the dyno - as usual

I will post up some dyno sheets and a recap sometime tomorrow when I can get to the scanner

In the mean time - check out this interesting tale

One of my good customers came in with his Evo fro a retune and test - his car was maiking only 211 whp with a intake - fmic pipes - 3" exhuast with electric exhuast dunp valve in the down pipe - and the Dyno Flash

We were shocked that he was making almost 100 whp less than when we tuned him a few months ago - which was odd b/c usually the Dyno Flashed ecu equiped cars come back to the dyno with the same whp they get originally tuned with

After some head scracthing and questioning of our client we quickly determined that he had entrusted his car and SAFC II to a buddy who did some "fine tooning" with the SAFC !!!

Turns out his buddy thought that more fuel = more power and he had put in like 25 % more air flow settings in the SAFC

The lesson here is DO NOT let anyone play with your SAFC or other piggy back who is not using an accurate wideband 02 sesnor

We removed the SFAC settings and his power jumped back up to approx 295 whp which was along the lines of what we expected on such a warm and humid night and with the dyno filled with mega exhuast fumes

Then we tested his electric exhuast cut out / dump valve which amazingly lost him 60 whp when we opened it up !!!!!

On the very next run we closed the exhuat valve and his power shot back up the 60 whp

Needless to say it seems that these electric exhuast dump valves are not very good mods on evos with stock ecus

The exact reason for the loss in power with the electric dump valve was not detrmined as we did not have time for dianositic testing as it was very late and everyone was ready to go home after 14 hours on the dyno. My theory is hat the super loud noise near the engine block could have triggered the knock sensor. In any event - I just thought it was an interesting story.

 

man that's crazy if it was triggering the knock sensor, this weekend at a car meet a very nasty sounding late sixties mustang rolled by me and my car almost died, same thing happens at the track in staging lanes when I'm near a very loud and lopey hot rod. happy his car is making proper power again, dude keep your bud the hell away from your safc.

 

Thats odd...with my stock Ecu... i produced 30+whp more and 20+more tq with the cutout open with the DynoFlash... opened i had 350+whp and close i had 320whp....

 

sounds like placement could be key with this mod, maybe he has his too close to the engine upstream in the exhaust Rollaway

 

thats why they say "don't race with your bumping music on"

 

he did - Rollaways cutout is closer to his test pipe, where as Henry's cutout was close to the front of the car. U could see it right infront of the front wheels under the engine bay.

 

This is hardly scientific - BUT - seems better to put the cut out further down stream

 

If you have a cutout that works the right way, how do you tune the car? With it open or closed?

 

Tuning it opened would sound about right.

 

no test pipe here.. stock cat is there... and i made emmissions

my cutout is located under my feet.. about 4inches before the cat