Flatspot

[wrinx]

Hope I'm not breaking some forum etiquette, not sure how strict you guys are about other models....but you do seem to know a bit about turbos

My 156 JTD has always had a flatspot from 3-4k revs....it feels like its struggling but will eventually get through.

But, if I floor it, the car just flies through the rev range.

It's been remapped but I've no idea how much except to say it's a lot faster than the 175bhp JTD I sold to buy this one. I'd guess 190bhp.

Any thoughts?

(If it breaks the forum rules please delete )

wrinx

[Steve Webb]

Has the car had anything else done to it other than the remap? Any idea who did the remap? Sounds like the the fueling might not be set up correctly for part throttle settings. Have you noticed any extra smoke out the back?

Steve

[wrinx]

Not got a clue about the remap, car was bought from a garage as a part chop. Don't even know what the exact BHP is

I wondered if it could be the throttle position doodah, have read of one or two needing replacing.

It does the same in any gear, between the same revs...only smokes at low revs when grumbling a bit.

wrinx

[cuore_sportivo_155]

have you checked the Squadra tuning website, they often report on dificulties encountered in chipping cars. Might be something about the flatspot there

[#84]

When you are in the range of 3-4k rpm on a Diesel engine of that size, boost pressure should be no problem, otherwise the smoke limiting device could give that kind of impression.

What I could imagine is that the engine reaches maximum boost and torque below this "flat spot" and you feel the steady, or even decreasing, torque as a flat spot.

ANother alternative is that the fuel injection timing is set to reduce the NOx emissions, normally later to reach maximum combustion pressure when compression i fallen a bit after TDC so that combustion temperature is recuded. What a re-map can do is the advance fuel injection - and ignition since it is a Diesel engine - which gives better performance.

I do not know how the certification test cycle looks like (I have it somewhere, but can't find it) but it is likely that they sacifice performance in this range to win performance where it looks better in the sales brochures.