Changed to a new exhaust - should I remap the engine?

[Grubbster]

I've recently swapped my 6" Powerspeed 4-2-1 system for a big bore Raceco 4-1 on my highly tuned K series (230 bhp). At the same time I replaced my ITG air filter for a new one, other than that I don't think I have done anything that could change the way the engine runs. It now feels a bit different - slightly more hesitant to start, lumpier idle, not quite as sweet when pulling through the revs and it seems much noisier (induction not exhaust).

 

I don't think I am imagining the differences and I know a 4-1 will be different to a 4-2-1 but would it be worth getting the mapping looked at or is this something that couldn't make the difference? Previously the mapping was spot on (it has an Emerald) - hot and cold starting on the button, pulling well and smoothly throughout the range so I'd like to get it back to where it was. The reason for changing the exhaust was to reduce noise (struggled on some trackdays), the primaries are the same diameter.

 

The air filter is not as deep as the one I took off (my mistake I ordered the wrong one) but as the backplate is fitted at the open end of the trumpets I didn't think this would matter as there is nothing protruding into it. Obviously I can stick the old one back on and see if that makes any difference, but I no longer have the old exhaust.

 

In terms of out and out performance it feels about right so nothing major wrong, but it is different and the induction noise noticeably louder (as anyone on the IOW last weekend will tell you )

 

Any thoughts?

[Adrian Williams]

I'd re-map it after a fundemental change like that.

 

 

[Grubbster]

Thanks Adrian, I must have just been lucky with the exhaust I had when I dropped the engine in, I've never had it mapped. I'll get it booked in soon.

[Adrian Williams]

Steve, I had mine re-mapped when I first had it and then mapped again when I had to run with the cat to meet MSA regs. So same standard Caterham exhaust both times but with collector or cat/collector and the map was changed quite significantly.

 

If you're planning any other changes no mater how minor get them all done first and then get it mapped.

[Birkin S3 ZA.]

Yes I would get it mapped again and may be get them to adjust the cams to get a better power and torque curve, it worked on mine and removed the dips in the curve.

The Exhaust ended up retarded from 3mm lift to 2,9mm and the inlet got moved from 3,5 mm lift to 4,1 mm lift at TDC.

Chris.

[peter clarke]

Yes, remap. Have used 4-1 and 4-2-1 on my 1600 K, only 180 horses, and needed remapping. I switched for more low down torque for road use,which it gave.

 

Did the Raceco give a significant reduction in exhaust? I ask as I am considering buying one to replace the 6" Techcraft one I have.

[Grubbster]

I think the exhaust is quieter Peter, I'll measure it sometime and find out. Hard to tell as I couldn't hear the exhaust at all over the induction!

[peter clarke]

Be very interested to know when you have solved other problems. My induction is very quiet as air feeds in thru the side of car below bonnet and thru ReVerie low noise piping to large filter and then to there carbon fiber inlet box which houses 90 mm trumpets