How to best make use of a rolling road for mapping

[diesel des]

So I'm booked in on Thursday to a rolling road to finalise my vems mapping. It's 100 quid an hour plus vat so I want to make best use of my time there. I have the stroker running well on the efr6758 and have just tweeked fueling and timing etc on the road but it's hard to do that while driving. I have made a set of det cans and have tweeked timing up untill I could hear some ping then brought it back a little. Afr is about right too. So I'm wondering what's best to do on the rolling road. Should I turn the boost down and optimise timing at a low boost then ramp up the boost and repeat? Are there any magic numbers to look at such as timing. What I'm thinking is there a minimum timing number which if I get to I should just back off the boost and run extra timing. Eg is less than 10 degrees timing and say 2 bar boost worse than say 1.7 bar boost and 15 degrees?

Anything else to look into? Again with det cans I can hear ping easily. I have calibrated my ear by advancing timing on petrol untill I could just hear that distinctive noise then swapped over to lpg and as it's higher octane the noise disappeared. So is any ping acceptable? I have found that I would get the occasional single ping noise that would take 2 degrees or so of retard to go completely. Power seemed to fall off noticeably too.

Also approx how much timing extra can you run with super unleaded? I'm on asdas cheepest at the moment when not in lpg.


Cheers des.

[UrS6 - IamS6]

Hi Des,

No help to your questions, but looking forward to your results. Your work on the engine is impressive.

[adam g]

When I had my car mapped recently, the operator asked me what my boost limit was, i.e. the max I would be willing to run based on the engine strength and aimed for that. He used the strategy of richening the AFR to about 12, then hit the target boost, then pulled the timing in, then leaned out AFR last. This is putting it simply, obviously there was some finessing of the fuel and timing when he was in the right ball park. I must add that prior to arrival I was running a generic base map so my timing was way off. Im sure there are other good strategys but this one worked well for me - coming away with an 80% power increase.

[diesel des]

Hi Des,

No help to your questions, but looking forward to your results. Your work on the engine is impressive. [emoji144]

Thanks!

[diesel des]

When I had my car mapped recently, the operator asked me what my boost limit was, i.e. the max I would be willing to run based on the engine strength and aimed for that. He used the strategy of richening the AFR to about 12, then hit the target boost, then pulled the timing in, then leaned out AFR last. This is putting it simply, obviously there was some finessing of the fuel and timing when he was in the right ball park. I must add that prior to arrival I was running a generic base map so my timing was way off. Im sure there are other good strategys but this one worked well for me - coming away with an 80% power increase.

Adam I suppose that's were I'm at. I have the boost at about 90% of max now so it's mostly timing I need to tweek.

But just because I can run 2.3 bar boost in the midrange should I? Or should I run less boost and more timing?

[diesel des]

Anyone else with comments. It's due for the rolling road tomorrow...

[GazzaG60]

timing makes more power from my experience than boost.

call me crazy but I like to map on the road. no substitute for real world

[gnutz2]

Do the bits that are very hard to do on the road first, like high boost ignition timing and go rich to start with.

Then if you have spare time sort out the cruise ignition timing.

[Rusty]

IATs will tell you how much boost you should run... worth logging them to see how increasing the boost affects things.

[adam g]

Adam I suppose that's were I'm at. I have the boost at about 90% of max now so it's mostly timing I need to tweek.

But just because I can run 2.3 bar boost in the midrange should I? Or should I run less boost and more timing?

I remember searching for a pointer myself on this subject when I tried mapping on the road. I couldn't find a rule as such but 12 -15 degrees seems about the minimum on our engines., Im sure the sweet spot is different on different engine set ups. For info my sweet spot was about 18.5 degrees advance at my 26 psi max, more timing and less boost dropped the power from this point, and that was with 2 degrees timing being pulled due to rubbish 70 degree IATs. With Tesco momentum I might add.

I think you will just have to try both options on the rolling road to see which direction you need to go, it shouldn't take long. Once you have done the base line run with your current map (make sure you save a copy) try upping the boost couple of psi with required timing adjustments to get rid of any det and see if power goes up. Then reload the base map and try the opposite, 2psi boost down, timing up.

Any det is risky in my opinion, it shows you are too close to the edge. I wrecked a head over the space of 12 months on my old 10v from running it with occasional pinging.

I'd be interested to know your results too.

[GazzaG60]

on the 20v you will wreck the pistons I think as that's the combustion chamber part.

lower compression allows for more timing up top. so bigger turbo benefits from lower compression.

like gnutz says run a little extra juice then trim it out. power comes with the trimming.

[diesel des]

First run it actually made 455 bhp but a bit of heat soak brought that back. Did get more torque though with extra timing and boost in the mid range but no more power. Nice flat power curve too. Goal was 500 ft lb and 450bhp so it's just about right.