DHC8FO

Just got my engine back together 250 mi. ago, have problem with acceleration before boost. Starting from stop there is a flat spot on initial acceleration, in pre boost mode. I have roughness in cruse when vacuum is lower. Checked blow off valve, going to go through vacuum system next week. Any other candidates for inspection?

I must say boost works real well.
-Mark

special tool

What is controlling your AFR?

mark944turbo

You are probably going lean or going rich for a split second. What chips do you have?

Perry 951

Chips, AFM/MAF/MAP, piggy back, fuel pressure, injector size, BOV/RECIRC type all would help.

Also, have you double checked your TPS adjustment? I had a very similar issue that I corrected by adjusting the TPS a little more.

DHC8FO

I'm not quite sure what I've got, as I've dug into it I have found several goodies. For example 274 webcam, It appear the chip has been changed in the AFM, I'll have to open it to see which one. The BOV is stock, TPS is stock. I'm planning to redo most of the vacuum lines monday, and check the TPS. I'll let you know what I find.

Thanks for the input

special tool

That makes perfect sense. I have used a similar cam, and the afr has to be dialed in - they are sensitive. Stock or common upgrade chips will give you a surge, but those cams move the power upwards, so the expected fuel is not necessary at 3000 revs.