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Dyno results, I need to take action!


Jake

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My car has been on the the dyno at Thor today.

 

The good news : At the hubs, my '93 Auto RZ made 350.5 Hp @ 5904rpm and 1.17bar, which I think isn't bad for a car which is completely standard apart from having both cats removed.

 

The bad news : Pete had to do my runs with a delicately balanced throttle to keep the boost below 1.2 bar because above that I've got a serious problem which the Air/Fuel Ratio and Detonation.

If given full throttle, at 4000rpm when the second turbo comes on song the AFR is 11.0, which I believe is OK, but it then rapidly rises and by the time the revs have reached just 4875rpm the AFR is up to 12.86, which Pete tells me is dangerously high.

His collegue (who's name I didn't catch) was checking under the bonnet at this time and said it was detonating badly.

 

Pete recommeded a new fuel pump and then a FSE if the pump didn't improve things. Unfortunately we didn't have time for him to fit any of these parts today.

 

If I post pics of the dyno plots perhaps you guys who know about these things might advise me whether I should improve the fueling somehow or whether I should just restrict the boost to 1.2 bar.

 

 

Aren't dynos great? I wouldn't have know about these problems until I blew the engine up if I hadn't done this today. You might say that I should have noticed the Det but I honestlycan't hear it from inside the car at speed.

 

--

Jake

'93 RZ Auto

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A question for those in the know - I have heard either 11.7 or 12.5 as being the ideal afr under boost. Which is it? I know stoich is 14.6, so 12.5 sounds decently rich to me, and Corky Bell recommends it in his book, but if Pete Betts thinks 12.86 is dangerous (whereas it would be edging towards borderline if 12.5 was the correct afr) I'd like to know what others think...

 

Post up yer dyno plots, Jake.

 

-Ian

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Just phoned the ever-helpful Chris Wilson and he says 12.5 is OK but aim for 11.7 to be safely rich, and I'll readily agree with that, especially with piggyback tuning. There are only minimal gains of power in leaning off to 12.5 and no adverse effects (barring fuel consumption lol) of running 11.7.

 

-Ian

 

Edited to finish the sentence, doh

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Well, judging by the red line graph, where you hit 1.3bar, the AFR was heading north scarily fast, good job Pete stopped :eek: The red line on the torque and power curves show a huge power increase because it was going so lean (extra power for a brief amount of time, then no power because the engine went pop).

 

The 1.2bar run, the blue line, shows a real tailing off around 6000rpm. If you got a restrictor ring and it deffo held to 1.2bar or less, but certainly no more, I still wouldn't take it over 6000rpm.

 

A beefier fuel pump would be a good idea - UK spec or Walbro. If you could fit that, and only that, then do the dyno runs again that would give the community a *very* valuable set of data.

 

-Ian

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Originally posted by Ian C

Just phoned the ever-helpful Chris Wilson and he says 12.5 is OK but aim for 11.7 to be safely rich, and I'll readily agree with that, especially with piggyback tuning. There are only minimal gains of power in leaning off to 12.5 and no adverse effects (barring fuel consumption lol) of running 11.7.

Wow, that's really good of you to ring Chris! (He'll be billing you not me, right?)

Interesting - thanks.

 

BTW, what do you mean by "piggyback tuning"?

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Originally posted by Ian C

The 1.2bar run, the blue line, shows a real tailing off around 6000rpm. If you got a restrictor ring and it deffo held to 1.2bar or less, but certainly no more, I still wouldn't take it over 6000rpm.

I've got a ring I bought from CW months ago, I'll pull my finger out and get it fitted soon.
Originally posted by Ian C

A beefier fuel pump would be a good idea - UK spec or Walbro. If you could fit that, and only that, then do the dyno runs again that would give the community a *very* valuable set of data.

You mean get it re-dyno'd after fitting the pump but before fitting the restrictor ring, right?

OK, that's what I'll do.

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Jake ... I had the same kind of result a few weeks ago on the Dyno. They didn't even do full power dyno run as the Det was sounding pretty messy (sounded like a bunch of keys jangling about).

 

Anyway - I'm having an uprated fuel pump, 550 injectors + SAFC2 fitted this week by Matt and the Vortex guys, so I'll let you know if that solves the problem :thumbs:

 

Cheers, J :cool:

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Originally posted by Jake

 

BTW, what do you mean by "piggyback tuning"?

 

These are electronic fuel/ignition controllers that fool the stock ECU by intercepting the signals, hence the word piggyback.

 

 

 

:thumbs:

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If i remember correctly for optimum power you want to run 10% rich over stoich which in most setups maybe considered a little to lean, people do run richer as the added fuel is a safety margin plus it brings the temps down as the unburnt fuel is also being used as a coolent.

 

:thumbs:

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Originally posted by Jake

 

Pete recommeded a new fuel pump and then a FSE if the pump didn't improve things. Unfortunately we didn't have time for him to fit any of these parts today.

 

M8 - have both of these sitting here

 

The pump even I could do - so go for it!!

 

:thumbs:

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Jake, that's exactly what I mean - fit the pump and do another run, obviously keeping a very close eye on the fuelling at 1.3bar and anything over 6000rpm. Get those dyno plots and upload them. Luckily the pump is under £100, I know Vortex have them in stock, as apparently does Paul "Vulture" E so I hear :D

 

It's an easy job if you've done it before :p The plastic ring thing is a bastard to take off (and put back on!) and the banjo bolt on the fuel feed pipe is hard to undo as the whole pump cage rotates instead, so have fun :)

 

Also I asked CW for my own purposes - tuning mine with the E-Mangleage. Just thought it would be relevant to this thread :)

 

Wez has piggyback tuning spot on, it's not a replacement ECU so it's never going to be as accurate to map. This, in my opinion, is only an issue if you are going for a full-on race setup, where 100% is only just good enough so you have to run a knife-edge map to get full power. Besides, the stock ECU runs very rich under boost anyway...

 

-Ian

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Downside to not doing the fuelling and / or restricting the boost.

Blown turbos / plugs / piston / ( engine rebuild )

Lot of work / lot of skin off knuckles / lot of exasperation.

I did exactly that with mine, as could not wait to blast it, it ran

lean and detonated, 4 plugs blown to pieces thru the pistons and second turbo.

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Originally posted by TLicense

For typical A/F ratio's under boost and at RPM's have a look at this courtesy of AEM EFI basics.

 

Regards

 

Tony

 

Just to add to that 100kpa is approx 1 atmosphere therefore 200kpa is approx 1 bar boost.

 

:thumbs:

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