Dyno Run

[Vaughany]

I have recently had my 1st Cat took out, fitted a Restrictor ring and had water injection fitted all by Chris Wilson. Today I went to Thor Racing to have the car dynoed and check the fuelling was safe.

 

I was pleasantly surprised that my RWHP has risen from 325 to 371RWHP and my torque has increased from 330 - 339LB. Not bad for stock twins running at 1.2bar.

 

My only concern was my AFR, the curve is good until about 4700rpm where it goes from 11.6 steadily climbing peaking at 12.3 at 5500rpm. At 5500rpm it then drops back down to 11.8.

 

Thor Racing told me that they could'nt hear any detonation but I am now thinking I need a fuel computer to smooth out this lean spot or at the very least an FSE to increase the fuel pressure so this lean spot is removed.

 

the AFR actually goes above 12 from 5100rpm to 5500rpm, do I need to be worried or is this ok. Since I now have added torque and BHP I want to enjoy the car but want to enjoy it safely. I already have cooler plugs, CW SMIC, Uprated fuel pump and water injection so I thought I would be pretty safe but I would appreciate your opinions on this.

 

Thanks

[Vaughany]

Sorry I meant 371 rhhp not rwhp

[Jake]

Originally posted by Vaughany

I was pleasantly surprised that my RWHP has risen from 325 to 371RWHP

Hi Vaughany,

How are you calculating the RWHP figure?

 

Was the previous figure (325) done on the Thor Dynapack as well?

 

 

EDIT: Sorry Vaughney, I didn't refresh before posting so I missed your reply about the RWHP/RHHP. I thought maybe you were using some formula to work out the RWHP.

[Jake]

Originally posted by Vaughany

My only concern was my AFR, the curve is good until about 4700rpm where it goes from 11.6 steadily climbing peaking at 12.3 at 5500rpm. At 5500rpm it then drops back down to 11.8.

 

Thor Racing told me that they could'nt hear any detonation but I am now thinking I need a fuel computer to smooth out this lean spot or at the very least an FSE to increase the fuel pressure so this lean spot is removed.

 

the AFR actually goes above 12 from 5100rpm to 5500rpm, do I need to be worried or is this ok.

As I understand it, an AFR of 12.3 is good.

Ian C and Chris Wilson have both said in the past that an AFR of 12.5 is fine. You could richen it up a bit (and lose a little power) but you really shouldn't need to.

 

I'l find the thread about my Dyno run, AFR was discussed in that.

 

BRB ............

[Jake]

Have a look at this thread mate :

 

http://mkivsupra.net/vbb/showthread.php?s=&threadid=21823&highlight=stoich

[Guest Terry S]

I would not be happy with an AFR of 12.3, 11.5 maybe, but not 12.3, what happens in the cold weather!!

[Vaughany]

Jake

 

Thanks for the info, that is a relief. At 12.3 they could not hear any detonation so that reinforces what you have said about an AFR of 12.3 being fine.

 

Thanks mate, you have saved me some money and a headache from the missus as I was looking to purchase an SAFC or at least an FSE.

 

Cheers

[Vaughany]

Terry, please elaborate on this please regarding colder weather. My AFR is above 11.75 from 4750rpm peaking at 12.3 at 5500rpm. At 5500rpm it drops back down to 11.8 but my bhp does not peak until 5750rpm. However my torque peaks at 5200rpm which is there or there abouts where I get this leaner spot.

 

Does this sound drastic or okay?

[Guest Terry S]

Right the stock ecu adjusts the fuelling according to IAT as long as you have enough injector/pump capacity. If however you have not the car will run leaner in the cold weather.

[Ian C]

Originally posted by Jake

As I understand it, an AFR of 12.3 is good.

Ian C and Chris Wilson have both said in the past that an AFR of 12.5 is fine. You could richen it up a bit (and lose a little power) but you really shouldn't need to.

 

I'l find the thread about my Dyno run, AFR was discussed in that.

 

BRB ............

 

Well, 12.5 is fine providing it doesn't get any leaner! It's maximum power but the margin for error is thin. 11.7 is what CW recommended I aim for, so then in different weather or whatever you've got a lot of headroom for changes in AFR.

 

Running 12.3 isn't going to wreck your engine, it does in fact give near best power. Trouble is, are you confident it'll stay at 12.3 or lower across all engine and environmental conditions...?

 

Consider this - when the ECU sees 1 bar of boost it's running the injectors at 100% duty cycle. So when you run 1.2bar and your FCD clamps it at 0.99bar to avoid fuel cut, your injectors are flat out. You get a cold day and 10% more oxygen in the cooler, denser air, your ECU cannot compensate for it by adding more fuel - it's already flat out. The AFR therefore gets leaner - if you are already at 12.3 it's gonna cause problems...

 

-Ian

[Jake]

This is a bit confusing. I was under the impression that stoichiometry for petrol engines was 14.7 to 1 and that using a richer ratio of (say) 12.5 was in order to allow a safe margin. No?

[SimonB]

Originally posted by Ian C

Consider this - when the ECU sees 1 bar of boost it's running the injectors at 100% duty cycle.

-Ian

 

That's true, but only at high revs. I did some logging with my shiny new E01 the other day and was quite suprised at how the duty rate ramped up with revs. I got something like this (all at > 1 BAR)

 

revs 4500  5000  5500  6000
duty 75%   82%   92%   98%

 

Looking at my dyno graphs, I was running lean at the 4000 to 6000 rev range, then fine(ish) at 6000 and above. So I've richened it up in that range, where there is still some spare injector capacity.

 

Obviously this is a temporary fix, I'm going to up the fuel pressure slightly with an Aeromotive and trim it out with the Emanage to give myself some headroom. I also have an AEM UEGO wideband sensor on the way - they do one without a display which is very cheap and will connect up to the E01 so you can datalog it along with everything else.

[Jake]

Originally posted by Jake

This is a bit confusing. I was under the impression that stoichiometry for petrol engines was 14.7 to 1 and that using a richer ratio of (say) 12.5 was in order to allow a safe margin. No?

OK, I've reread that old thread and this is what Chis actually said :

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

so I guess the lower AFR would allow for atmospheric changes. I think I understand now.

 

 

Edit:

So where does this leave Vaughney? He's ok at the moment but should get it richened up a bit for the cold weather?

[Ian C]

Stoich is 14.7:1 at idle and cruise, but things change under boost. A lower AFR is required otherwise detonation will occur. This is why you cannot tune your fuelling off the stock narrow band O2 sensor - it will be reporting rich at 14:1 AFR when in fact that's dangerously lean while under boost.

 

You want 12.5:1 for best power, 11.7:1 for safety with minimal loss of power. Another handy figure is maximum duty cycle - you want to see no more than 85%, although from what I can figure, plenty of Supras have been running at 100% for ages, gawd bless Toyota.

 

Duty cycle rockets up as the RPMs increase, not because you need more fuel but because the time the injectors have got to deliver it drops. SimonB needs bigger injectors Vaughney probably does too! Upping the fuel pressure changes the fuelling across every load site on the map - idle, cruise, part-throttle, low boost, WOT. It's a wretched way of "tuning" your fuelling.

 

-Ian

[Guest Terry S]

You see I would disagree, the leanest i would tune a car is 11.5. This is a road car not a race car. I would absolutely not want to do a sustained Motorway pull at 12.5 AFR

[Ian C]

Agreed When I said "best power" I meant it in a motorsport-aftermarket-programmable-ECU fashion. Road car = aim for 11.7 or lower

 

-Ian

[Guest Terry S]

remember the rule of thumb.....most power is on the verge of destruction:thumbs:

[Jake]

Nice one guys. Thanks for the explanation.

 

So Vaughney, looks like you do need to sort your fueling out after all mate! Sorry for the mis-information earlier

[SimonB]

Originally posted by Ian C

SimonB needs bigger injectors Vaughney probably does too! Upping the fuel pressure changes the fuelling across every load site on the map - idle, cruise, part-throttle, low boost, WOT. It's a wretched way of "tuning" your fuelling.

 

-Ian

 

Yes, but so does fitting bigger injectors. In either case you need to trim the fuel down everywhere apart from where you want the extra using an SAFC or EManage. For a modest increase in fuel I can't see the advantages of bigger injectors outweigh the extra expense.

[Guest Terry S]

Originally posted by SimonB

Yes, but so does fitting bigger injectors. In either case you need to trim the fuel down everywhere apart from where you want the extra using an SAFC or EManage. For a modest increase in fuel I can't see the advantages of bigger injectors outweigh the extra expense.

 

I agree with this to a fashion, but long terms it is a bit of a fudge. Having said that there are a few firms which do conversions to cars which do exactly that.

[Vaughany]

Can anyone shed any light why I would get the lean spot from 5100rpm to 5500rpm (AFR of 12 - 12.3) Thereafter from 5500rpm - 6500rpm+ the AFR drops back down 11.8. It is only for this 400revs that the AFR raises to above 12.

 

Before 5100rpm my AFR is at is a little rich, at 4000 - 4250rpm, 11.01 (possible due to walbro fuel pump) After 4250 it is between 11.25 - 11.8 all the way until 5100rpm. The only problem I seem to have is from 5100 - 5500rpm where it is 12 - 12.3 AFR

 

I am awre that I may need to get some adjustments done to lower the AFR between this period. Would you recommend an FSE or equivalent piece of kit. Does the FSE only raise fuel pressure when boost raises requires extra fuel so I wont be running rich at lower boost or a idle revs?

 

I hope this makes sense.

 

Thanks

[Vaughany]

Dont worry Jake for the misi nformation. Can someone do me a favour, come around and tell my missus that I need a SAFC. i dont want the headache.

 

Only kidding, Terry do Vortex sell the SAFC, how much arew they and what sort of price am I looking at for supply, fit and setup?

 

Thanks

[Ian C]

Originally posted by SimonB

Yes, but so does fitting bigger injectors. In either case you need to trim the fuel down everywhere apart from where you want the extra using an SAFC or EManage. For a modest increase in fuel I can't see the advantages of bigger injectors outweigh the extra expense.

 

Oh aye, yes, I just meant the "up the fuel pressure job done end of story" approach was wretched

 

As soon as you start messing with the fuelling you've gotta fork out some cash on a controller and the associated mapping costs. If you want to stay below 85% duty cycle it's bigger injectors time. If you want to push the stockers beyond their normal limit, fit an adjustable FPR and up the line pressure. The adjustable FPR is easily the cheapest option and a lot of cars run it - it's up to you.

 

-Ian

[TLicense]

I have a warlbro and FSE, and at 6500 rpm and 18 psi my injector duty is 80.something %. It does ramp up a lot after that, for example at 7000 rpm it's at it's about 90% and at 7700 it's at 99%

 

However my AF ratio's are a smidgeon high at between 11.7 and 12.7 AFR.

[dandan]

My personal thoughts...

 

Assuming worst case scenarios (ie most possible airflow through engine - highest boost, highest atmo pressure, most heat soak etc etc) I don't think an injector duty cycle of 90-95% is as terminal as people make out.

 

Most injectors are capable of running at close to 100%. Although not ideal, it is not the most disgraceful scenario that people seem to think. I would not choose to map a custom fuel setup with 100%DC however (more like 75%) - It's nice to future proof with a little headroom. However, if 95% is the worst the injectors will EVER see then I would not be overly concerned.

 

I've been in discussion with one particular UK ecu manufacturer regarding a completely new custom ecu (plug n play) for the Supra as well as another car I am working on, and they have some interesting opinions on injector duty cycle and fuel pressures. 100% duty cycle at total worst conditions for det and lean-ness is not considered terminal.

 

As for fuel pressure, I believe that the touring cars (not sure if true for the current season) have to run the stock fuel injectors. The likes of the Nissan team would run a comfortable 100+ psi rail pressure with no ill effects on longevity or spray pattern with the stock injectors. I think the Nissan injectors we're pretty impressive though in this department (reliability); might not hold true with the Vauxhall's for example.

 

Something to consider perhaps with all the talk of "band aid" increased fuel pressure solutions?

 

*I am not a great fan of rising rate fpr's though. (I don't mean boost referenced types!) This in my eyes is a little bit of a bodge and makes mapping quite tricky. However, in some cases it does do the trick and serves a useful purpose.

 

It all depends on your aims, what you are happy with and how much you have to spend.