My car (s4t) used to run, and drive great with the old motor and ignition map. When the motor bit the dust, I had an S5 rebuilt/street ported and put that in. With the new ported motor, I had to change the old map quite a bit to get it to idle steady, and have a smooth idle/light load transition.

There is one bug I can't work out, the car badly bogs on up shifts. If the car is idling and I rev it, it will rev cleanly. If I am holding it at a steady RPM, and rev it, it revs fine. The problem is if the rpm's are falling, and I blip the throttle, the car will bog badly, and will almost die. The bog is usually met with a small back fire when the motor "catches". This makes up shifting smoothly quite difficult, and matching revs on downshifts almost impossible.

The motor has about 100miles on it, so I am keeping it under 4k, out of boost. Any help/tips would be greatly appreciated. I don’t have a laptop, or wideband, only the dash unit.

 

it just sounds too lean in the 10,5 and 0 maps, add some more fuel to them and see how that goes, you may also have to add some fuel to pump1 and 2

dale

 

Doesn't back fire normaly = rich?

 

depending on the back fire,

if it is coming out of the exhaust it generally means it is rich but a bad flat spot and pop from the intake means it is lean,

dale

 

thanks for the replys.

The back fire is comming from the exhust.

adding fuel to the 10, 5, 0 maps didn't really help. I was adjusting them in the idle map. should I be using the load map? please bear with me as I am a bit timid with this tuning thing, especially after forking out the cash for one rebuild.

It seemed to get a little better when I added some fuel to pump2, but the problem is still there. I went up 6%, on pump1, and pump2. how much is too much?

After changing spark plugs, and making a few adjustments, it will bog now when i hold at a steady RPM, and blip the throtle. I noted the values before I monkeyed around, and even after I changed them back, it keeps bogging.

Now I have 108 miles on the motor now, so I don't really want to have it tuned by an expert, than have to go right back in a couple months for load tuning, and pay twice.

 

DO you have fuel cut on deceleration turned on? if so, turn it off and see if the bogging goes away.. if it does go away, then chances are you have some lean spots in your map as well as increasing pump 2 will help.. but turn off the fuel cut on decel first...

 

you will need to add the settings in the load map, the idle map only works when the throttle is closed

just start it up and add 10% to the mixtrim and see if that fixes the bogging, if it does it is too lean, and you will have to add fuel to the maps.

Dale

 

thanks a ton.

Adding fuel to the mixtrim fixed teh bog. adding a little fuel to the load map got it even smoother.

 

execlent,

just add some more fuel to the idle and load points so you can but the mixtrim back to 0%

Dale

 

I find myself using the mixtrm alot. It's a good tool, use it to determine what the engine wants, then make the adjustments in the map and put the mixtrm back to zero.

 

cool, I'll give that a shot tonight.

 

ok, to get the car running good, I had to add 22% with the mix trim. However, I am getting some surging at constant throttle.

Since I went up 20% with the mix trim, do I go up 22% of the values on the load map? to get the mix trim back to 0.

 

the surging at part throttle is probably too lean, just add the 22% to the values and then add some more to get rid of the surging in the 20 and 15" screens

Dale

 

OK, I'll give that a shot tomarrow. Let you know how it goes.


Is it normal to have to add this much fuel for a street port? I have stock injectors.