Dyno Graphs

[carlmthompson]

Okay, trying to make sense of these, so I have a few questions as you might expect:-

1) Car is making 259BHP (good thing!), but the boost is at @11bar, which I thing works out to around .75PSI, or .07 short of where it should be. Does this point at the waistgate starting to be weak, and if so, is it really that weak?

2) According to the graph, the highest Torque point is 216Ft Lb - this is obviously well short of what should be 258. Any ideas why, or this normal on the Dyno?

3) How the hell do I interpret the AFR Graph?

 

[Hilux]

11 psi, just under 1 atmosphere (15 psi = 1 bar)

I`m sure I`ll be corrected by our technical boffins but the cars run at or v near 1 bar boost when new.

You may be looking at the wrong graphs.

Mine made 2471b ft at 253 bhp at the flywheel and 213 and 208 at the road wheel

I assume the AFR graph is a percent of fuel in air, in which case I`ve got a huge dip at 4000 where my max boost is so I interpret that as its not fuelling enough (potential leaning out which is worrying) at that point or its overfuelling everywhere else.

On the other hand..................calling Rick, Mr Sims, Fen..................................anyone??

 

[John Sims]

The dip on the AFR graph is an increase in fuel not a decrease. It is the ratio of air to fuel - ie 14 parts of air to 1 part of fuel is leaner than 10 parts of air to one part of fuel.

 

[Fen]

Standard 250 cars should run 0.82 bar over atmoshpere (1.82 bar absolute, which is what the gauge should approximately show). 1 bar is 14.73psi, so you can convert between the two using that.

The 4 graphs you got show flywheel power vs. flywheel torque, vs. air fuel ratio (expressed as AFR or parts air to parts fuel), vs. boost (in psi) and the last showing rear wheel power vs. rear wheel torque. This is the one with the lower bhp figure in the top right.

The AFR one is possibly the only one needing much explanation. 14.7:1 is stoichiometric ratio, which is the ideal mix for burning petrol/air at peak efficiancy. AFR is often quoted without the ':1', so add that to the number to make the correct notation. anything over 14.7 is lean, and that is bad on a dyno graph as it can lead to high cylinder temperature and detonation. Even running 14.7, although it makes most power and least emissions (on cat-equipped cars anyway) will make the cylinder temps too high and the engine will not last long, so that is left for race engines with a rebuild schedule in the single figure hours rather than 200,000 miles. Ideally then you are looking for the AFR plot to be a flat line across the whole graph, probably around the 12.5 mark on the scale. The bottom of the graph is rich and anything 13 or above is probably getting a bit lean for a road going turbocharged car on a dyno.

The other way of expressing air fuel ratio is the lambda scale. I can't find the Greek lambda symbol on my PC, but it's an upside down y. On that scale stoichiometric is represented as 1.0 and anything below 1.0 is richer, above 1.0 is leaner.

Cat equipped cars on a constant throttle (i.e. cruising) maintain stoichiometric ratio (running "closed loop") by measuring the AFR with a lambda sensor and dynamically adjusting fuelling to achieve it. That is necessary to maximise economy and effectiveness of the cat. On wide open throttle even closed loop cars ignore the lambda sensor and use the fuel map in the ECU, hence it can be played with to alter the performance of even a cat equipped car.

 

[944Turbo]

I think a lower torque figure on a standard engine may be attributed to engine wear (poor seating of valves etc.) .
On a modified engine it is more to do with efficinecies of intake and exhaust length, etc etc.

A weak wastegate will limit the peak boost you can hit and what you will hold. Boost leaks will also affect this. Generally lower boost than the engine management expects will result in a richer mixture.
Tony

 

[Fen]

I forgot to answer the wastegate question. Yes is the short answer, it probably is that weak.

The OE wastegate design is "single port" which means that boost pressure is fed in one side of a diaphragm and the only thing stopping it from opening is a spring. To give a degree of electronic boost control the cycling valve prevents the wastegate diaphragm from seeing the boost pressure until the KLR ECU tells it to open, which is OK except that the boost pressure being held in by the wastegate valve pushes against the spring also and can unseat the valve, bleeding boost. Because over time the spring gets weakened through use and high temperature that happens much of the time with a 15 year old standard wastegate.

The upgrade is a dual port wastegate which has a second port on the other side of the diaphragm. In this case some form of boost controller is required to balance the pressures across the diaphragm (so keeping the wastegate valve shut) until the desired boost pressure is reached, at that point the pressure on one side of the diaphragm is allowed to overcome that on the other and the wastegate to open.

 

[944turboS]

Great explanations for those of us a little less techie, how should we view the AFR plot if there is no turbo in the equation? Should we also be looking for a level line about 12.5:1?

 

[sawood12]

I reckon on my car the dual port wastegate is worth 20bhp. My car is standard apart from my Janspeed exhaust and Dual port wastegate with Manual Boost Control. I thought i'd set my peak boost to 0.8 bar which is 0.05 bar above standard for a 220 turbo but looking at my plot from yesterday I appear to be peaking is 0.75bar exactly. My car achived 240.0bhp so circa 20bhp is roughly what a single port wastegate is costing you. Acutally in reality it's even more than 20bhp as I never dyno's my car before I replaced the wastegate so i'm basing that assumption on the 220 bhp the car should have been developing off the production line. Therefore in reality the DPW is worth more than 20bhp on a 15yr+worn wastegate as before the DPW install I bet I wasn't even getting 210bhp as my wastegate housing had a dirty great crack in it meaning the wastegate was leaking even when the wastegate valve was closed. I think a DPW is a superb mod and i'm glad i've started with it as I feel i've got a good base from which all future mods can work to their best from. It'd be interesting to see what effect a DPW would have on Hilux's car which is getting a shade over 250bhp. If he were to see the same benefit on his car that I appear to have then he could be getting upto 280bhp in one easy step on an essentially standard 250turbo car.

And looking at how rich my car is running there is alot of scope for releasing extra power just by better mapped fuelling. I'm even more determined to go for a MAF running 1 bar boost which I reckon would achive 270ish bhp with all the other benefits a MAF will give. However it still puts me in the Vauxhall Conference of 944 modifing judging by some of the cars that yesterday that were getting around 400bhp. Not too shabby for an engine designed 30 years ago and orignally conceived as half a V8!

 

[Fen]

ORIGINAL: 944turboS

Great explanations for those of us a little less techie, how should we view the AFR plot if there is no turbo in the equation? Should we also be looking for a level line about 12.5:1?

I'm less certain of this as my posting was largely the result of talking to people like Chris at Weltmeister specifically about my car, but logically a normally aspirated car should run similar AFR figures as it's using the same fuel for the same purpose and AFR is directly related to the fuel properties (stoichiometric for top fuel dragsters is not 14.7:1 in other words). Perhaps it can go slightly leaner than a turbo as the cooling effect of fuel is less necessary when the intake charge has not been compressed and therefore heated before reaching the cylinder? Hopefully someone more familiar with NA tuning can comment.

Whatever the ideal value it should most definitely be a flat line and will be at around 12.5:1 ratio or slightly leaner.

 

[burrow01]

λ on my 993 printout starts at 1 and then falls away to 0.8 at max power. Any idea if this would be the result of the mapping ignoring the λ sensor at full throttle, or could it be running rich?

I'll also ask on the 993 forum to see if anyone has an equivalent graph for comparison

cheers

Pete

 

[Fen]

Your's is the chart exception to the rule; WRC/Weltmeister use lambda, but Rick uses AFR in his league table so everyone else got AFR as the right hand scale.

Anyway, that's a nice AFR plot. I guess I simplified slightly in recommending a straight line - most will be leaner at the left hand end where the load (and power and torque) are lower. Your plot would indicate that your car is running about 11.8:1 AFR at the top end. 12.5:1 is 0.85 lambda. Which is a bit rich, however.

edited as on reading through I realise I forgot to mention the richness - nice line, but could have been further up the axis I think

 

[Diver944]

I just love these post dyno day graph discussions [] they can go on for weeks and will.

I can't wait to see all the graphs on Ricks site (maybe I should have been a statistician [8|])

 

[burrow01]

ORIGINAL: Fen

Your's is the chart exception to the rule; WRC/Weltmeister use lambda, but Rick uses AFR in his league table so everyone else got AFR as the right hand scale.

Anyway, that's a nice AFR plot. I guess I simplified slightly in recommending a straight line - most will be leaner at the left hand end where the load (and power and torque) are lower. Your plot would indicate that your car is running about 11.8:1 AFR at the top end. 12.5:1 is 0.85 lambda.

My car went on first, before the graphs were switched to AFR for the 944 runs - thanks for the interpretation []

Cheers

Pete

 

[Hilux]

Fen

That bit you found (ally pillar/tower), which bit was it?

I reckon it was your no 3 con rod or the crank broke around that point?

 

[carlmthompson]

ORIGINAL: Hilux


You may be looking at the wrong graphs.

Unfortunately not - it made 218/180 at the wheels.

The boost graph probably tells half the story - it makes 11psi @ 4500, but tails down to @ 9psi by 6700rpm.

I would have thought however that there would be a lack of HP to go with the lack of Torque?

The AFR graph is also al over the place - starts of at about 11.8, falling sharply down @ 4500rpm to below 10, then steadily up again from 5500rpm to 12. At least it's not lean! Would I be right in thinking this could also be caused by a weak waistgate?

Anybody got any suggestions as to why the car still makes good HP with low boost?

 

[Hilux]

Here`s my AFR, it appears to enrich itself between 4 and 5500 so is probably losing power at that point yet the power curve is linear ie: there is no dip its a nice smooth curved progression.

Is this a poor mapping issue?

Interesting point re DPW as the boost on mine (typically) tails off.

It seems that at max boost it overfuels, seems sensible but is it right?

Interestingly there is a slight blip at 4000 where the power rises briefly as it starts to overfuel just as the turbo cuts in, is this to stop it leaning out as more air is introduced?

Edited to say that RH this year was 74, last year 15 and amb air temp was much lower too (hence 3bhp increase??) []

 

[Hilux]

Unfortunately not - it made 218/180 at the wheels.

259/218 = 19% power loss. Mine was 253/217.3 = 16% (1% over factory standard) [Incidentally mine made 208 lb ft at the wheels (15.5% above yours) so you have an issue somewhere]

Could be dragging brakes, wheel bearing, sticky gear box oil, slippy clutch................................handbrake on [][][]

Find the dragging loss and it could add 3% to your power figure which would be nearly 267bhp [8D][8D] but I`m not sure where your torque has gone unless its a 220 engine or turbo and runs out of puff.

 

[Fen]

ORIGINAL: Hilux

Fen

That bit you found (ally pillar/tower), which bit was it?

I reckon it was your no 3 con rod or the crank broke around that point?

I think it was the leftmost post in your picture that Tony found on the crossmember or wherever. I tend to agree that the crank is broken because I really don't think I had the clutch in quickly enough to coast right away and aside a very brief snatch that felt like a misfire the car coasted beautifully. I'm itching to see it on a ramp with the undertray off get some pictures of the damage from below.

I'm thinking it was #4 rather than #3 as the back corner of the block looked to be missing and the crack on the other side is quite far back, behind #3 intake runner. That would also concur with the free-wheeling if the crank broke toward the flywheel end, if it broke at #3 then #4 would have been flailing around on the broken crank stub.

I think for sure it will be a mess in there and I'll post pictures when I have them.

 

[Hilux]

*cough*

I have a spare sump if you can find a block [][][]

LS1 ???

 

[carlmthompson]

The rear brakes are most definately a bit sticky!