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Strategies for Dyno Tuning


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I just wanna see the graph, for pure interest. I am MAINLY concerned with HOW much drive train loss there actually is in a TKO, down to a R200 diff, and then out to the wheels. I just find it interesting that the dyno guy knows exactly how much drivetrain loss there is. I have no need to be a "top dog" Or anything like that. I build my cars to the best I can, thats it. I am ALWAYS wanting to learn more, thats why I asked. If you took it another way, sorry for that. Age has nothing to do with it, what so ever. I have ZERO experience with a MAF, everythign I play with is MAP, thats why I asked, instead of told. I wish we could all find out exaclty how much drivetrain loss there actually is, but with so much discrepency in dynos, is it possible? I wonder if we took a known motor, put it on a dyno, measured, then installed a trans to it, then measured it, that would tell us how much on the trans. Then do the same thing with a differential. Then we could get a good baseline for what these drivetrains actually have. 658/537=22.5% increase. I know that like BIG heavy gear boxes, and big diffs draw about 20%, so I was just wondering if the TKO has alot more drag? I have always heard people say about 15% drivetrain loss. I am here to learn Jeff, please stop taking things the wrong way.

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No.

 

The further upstream the MAF is located (meaning closer to the air cleaner) the more susceptible it will be to 'puffs' of air making it get a false 'high airflow' indication and transmitting bad data to the ECU.

 

You are taking it from an area where there is not airflow blowing on the element. The wheel wells are actually lower pressure.

 

If you remember a few years ago on GRM 2000 Challenge there was a Z31 with the MAF stuck through a snorkel in the hood facing forward. This gave the car 'Full Rich' when moving. In that case, the MAF could read significantly different numbers if you were driving into a 30 knot headwind than going in the other direction with the wind at your tail. In such a setup, a stiff breeze might indeed make the car run rich enough at idle to stumble. Explain that to someone...your car died because the wind was blowing too hard!

 

My kid was like 4 years old when I 'Blew Out The Fire' on a Ford Thunderbird. Picked up the MAF and blew into it, car died. Restarted it, and let him blow into it, and he killed the engine as well. MAF's are VERY accurate at reading airflow---this can be good and bad!

 

This is why most MAF systems have defined runs of piping before and after the sensing element, and why most performance mods center on removing the prepiping and belling a smooth entrance to the MAF (JWT or HKS POP Charger style)---any little change in throttle will cause the MAF to read and richen with these setups. It takes out the engineered deadband in the operational characteristics of the sensing element making it more responsive to changes in airflow.

 

I totally stated that incorrectly, I meant locating the maf further from the air filter.

 

In any event, sounds like its fine where it is in my car.

 

Thanks guys, good read here.

 

Evan

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Brian, that was a great response to jeff's wee rebuttal. Your initial comment DID come off as a little sarcastic, and please keep in mind that JeffP has taken a BARRAGE of "I call BS" on his dyno numbers, so a touch of sensitivity on his part regarding this is certainly excusable. :)

 

I think this is a demonstration of the second half of the phrase "A little knowledge is dangerous.. and so is alot." You guys both do know alot, so each can seem to the other as if they have a bit of "know it all" in their makeup, when in fact its just a mis-judgment of tone. Black and white text has no voice to it, so it is easy to read sarcasm or pride where only jest and confidence are intended. The difficult part lies in making the tone more abundantly clear in any posts here.

 

 

On a side note, I have to remember that "blowing out the fire" bit for when my nephew gets a few more years on him. Tony, I am sure your kid was fascinated by the discovery of such a possibility :rolleyesg

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>Ok 5% loss through the drive train @ 658hp=625hp 10% loss=592hp 15% loss=559hp 20% loss=526hp I posted a run that stated 537Hp @ the wheels with 509 foot pounds of torque, that was not the final WOT run, so you tell me.

 

Jeff is being conservative with those numbers and the response. The 'high end numbers' he has dynoed on the Mustang are known to probably three people on the face of the planet, and one of those probably has forgotten them already.

 

The statement about 'proof' was uncalled for in the first place.:sour:

Mainly because the engine is still undergoing development. It was only an 'interim' number to show the progress.

 

As I recall, there was a goal set of 600 CRANK HP rating at the outset of his project.

 

I can say, from personal observation of the dyno runs that unless there is some magical way that drivelines generate horsepower (negative driveline loss percentages) I can catagorically state the following: "JeffP's original stated Horsepower Goals for his buildup have more than been reached."

 

He's 'just fiddling' now, curious as to what other things he can do with the engine flexibility wise.

 

[/Threadjack Warning]

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I am here to learn Jeff, please stop taking things the wrong way.

 

Maybe a different way of stating that would be benificial (to rephrase it, quit putting it the wrong way!). Like putting what you JUST posted in the second followup post instead of posting "658HP??? Any actuall documentation of this?" Sure looks like a call of "B.S." to me. Especially the scoffing way the MAF item was phrased in the same post. Frankly, the follow up post looks like a coverup to the original intent. I don't see any reason the SECOND post could not have been posted originally, if the intent was really ONLY to 'learn'. "Age has nothing to do with it, what so ever." ---That may not be true at all, in fact it probably is more true than you are willing to admit. Perhaps with age comes a tempering of word, and subtlety of phrase that few youths posess.

 

Just a thought.

 

 

The second point is that you are the one with the dyno...so it would be far cheaper for you to do the work and find this out than having more R&D done by Jeff just for your curiosity's sake.

 

If people are curious, they should put THEIR money where their curiosity is... I know when the Wind Tunnel Testing was in the works, I put my money up...

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Yes there is a difference between a 4' fan blowing on the front of my car then driving down the road. The hood is open on the dyno, and there is a much smaller amount of air going across the radiator on the dyno. AND I am very happy that is the case. The car will run into the 100-110 degree C water temps in no time on the dyno, interesting enough, I don't have that problem on the road. And yes there are times with a good cross wind on the freeway I do get the occasional surging. That is just the nature of a MAF, and it's location.

I completely agree - the difference between a 4' fan and driving down the road is huge. If you don't believe this, go back and look at the fan used in the wind tunnel tests - that's what you need if you want to simulate real-world airflow through the engine bay.

 

While I wasn't having coolant temp problems in my last set of dyno pulls (I've gone back to the mechanical fan), I was seeing very different manifold air temps - on the order of 150 degF peak vs 105-110 peak at max boost on the road. The intercooler simply heat soaks on longer dyno pulls.

 

Next time I go back, I'm going to try a few pulls in 3rd vs 4th to see if that helps - 4th should be the most efficient from a drivetrain loss point of view, but 3rd would give the intercooler less time to heat soak, and might give more comparable performance to the real world.

 

Now they also had an engine dyno at the shop they test engines on, I did not want to take the time effort and money to dyno the engine that way.

 

I know Jeff was being somewhat facetious here, but I don't think this would prove anything anyway. Everybody seems to think that there is such a huge difference between Mustang vs Dynojet to the point where a Dynojet is now "useless", how are you even going to begin to quantify the differences between these two completely different measurement methods? (JeffP - this is not directed at you - I believe I already saw others suggesting this or something similar as a method for verifying drivetrain loss). I generally don't even try to talk about how the power at the wheels translates to power at the flywheel - it just generates more confusion.

 

Back to tuning - on gas, my EGTs did run cooler at 11.5 AFR than they did at 12, and there wasn't any additional power to be had at 12 for my setup. I think that what you need for AFR is very dependent on you setup - cam specs, turbo sizing, head design and CR all play into this too. Full disclosure here - my EGTs at 11.5 were still very high, probably considerably higher than what Jeff was getting - just wanted to point out that running 12:1 AFR vs 11.5 didn't help in my case.

 

Also, somebody mentioned allowing a cool down between runs - this is very important. I generally monitor my MAT, and wait for it to drop back to the same temperature before starting the next run.

 

Brian, that was a great response to jeff's wee rebuttal. Your initial comment DID come off as a little sarcastic, and please keep in mind that JeffP has taken a BARRAGE of "I call BS" on his dyno numbers, so a touch of sensitivity on his part regarding this is certainly excusable.

 

I got the same crap the last time I posted dyno numbers, and it is very frustrating. I even got accused of fudging the dyno cals to get higher numbers, and one "genius" even claimed that there was "no way" that I was making over 300hp. I guess I must have changed the cal in the middle of each pull so that the off-boost numbers wouldn't look suspicious. Whatever:rolleyesg. The end result of that was that I don't post or try to help out nearly as often as I used to. Has anybody noticed that Jeff doesn't post that often, either?

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What we would do when I was stationed in Japan was go to the LOX plant on a Friday, and 'borrow' a bunch of CO2 fire extinguishers that were in for service. They all had to be discharged anyway, so that we brought them back empty on Monday made the guys at the e-shop happy anyway...

 

We would chill the intake manifold and intercooler with copious blasts of CO2. Having thermocouples in the air stream (er...let's not discuss parts soucring now...) to verify you have cooled it down.

 

This made for some consistent runs relatively quickly. A quick blast across the radiator did wonders for helping keep it cool during long pulls as well.

 

When they started marketing NO2 and CO2 based intercooler cooler systems for cars in the past 2-3 years, I just started laughing...we were doing this in 1985! I'm sure some other airmen were doing it before us, I know using CO2 to chill-freeze a beer keg on the boom of an MJ-1A bomblift is as old as the hills...

 

What I found works well is if you can find an old "Swamp Cooler" and them make a custom duct for the front of your car. Put it on a dolly so you can wheel it around...but it's just another huge thing to cart to the dyno. But you can get 10,000 cfm fans that will direct a lot of air into a small area with decent static pressure---far better than what most dyno shops have. And sometimes they want to buy your mostrosity or 'offer to store it for free' after they see it in use!

 

We put a separate radiator into the Bonneville car for dyno pulls. It is a custom 5-pass radiator that Andy had made to cool his 502 Caddy engine... "It works well" LOL

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speed density cars don't change that much in terms of dyno ar vs street. mas air cars freak. at least my ss does. my street afr is wildly different than dyno afr. i usually spend about 3-4 hours on the dyno at a time with my car. i like to test different things. dial in the afr, then tweak the timing down low. up top. so on and so forth.

 

now. with that mindless banter being said. every engine behaves differently. every engine will like something different. your car may make peak hp at 12.8 vs someone else's at 13.4. same thing would go for torque. too many variables. hence why a dyno is useful. same thing goes for timing as well. some cars like a lot, some like a little. this is where egt's come into play. sort of.

 

 

cram as many fans in front of that car as you can. dyno numbers vs street numbers vary. depending on the car, vary greatly.

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speed density cars don't change that much in terms of dyno ar vs street.

 

Maybe not from certain aspects, but from the aspect of heat soaking they sure do.

 

I think we're all in agreement that different engine designs have different needs. I've messed with enough different cars and engine types to know to pick out what the nominal timing setup is for each car as a basis to start tuning. Doritos (rotary) like 10.0:1 whereas Mitsubishi 4G63 likes 12.8:1 or leaner on pump gas.

 

IMHO EGT works as a great tool on a factory EFI'd car. When the engine detects knock (before you can hear it) it will pull some timing and make EGT's higher. This tells you right away the engine is getting heat soaked or there is something wrong, etc. On a standalone car it can 'sorta' give you a feel for what kinda timing the engine likes, but it has to be used in a meaningful comparison against other similar setups on the same engine.

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cram as many fans in front of that car as you can. dyno numbers vs street numbers vary. depending on the car, vary greatly.

 

Yup. Ultimately it's only good for a before/after comparison in similar conditions on the same dyno. Absolute "crank hp" estimations are pointless except for bragging rights. Run it on the track or strip; that's the real measurement of performance.

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Yup. Ultimately it's only good for a before/after comparison in similar conditions on the same dyno. Absolute "crank hp" estimations are pointless except for bragging rights. Run it on the track or strip; that's the real measurement of performance.

 

 

 

FINALLY Someone other than me POINTS THIS OUT.

 

 

JEEZE.

 

 

Its about a car as a system. This so called 22.5% drivetrain loss comment is pointless. Run it down the drag strip, ONCE and make a 10 or less second pass, then we can see how a car works as a system.

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FINALLY Someone other than me POINTS THIS OUT.

 

 

JEEZE.

 

 

Its about a car as a system. This so called 22.5% drivetrain loss comment is pointless. Run it down the drag strip, ONCE and make a 10 or less second pass, then we can see how a car works as a system.

 

When I bought my Dynapack AWD dyno back about 4 yrs ago they said the same thing.

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That makes the assumption that the 537 rwhp pull is the one he's referring to in relation to the 658 number. It was you who assumed a 22.5% driveline loss.

With as many pulls as JeffP has made, he is wont to cite numbers he has 'backup' for, but in some cases the dyno doesn't capture this run or that because the operator made an error in selecting which mode to run in, or simply was incompetent and didn't 'save run to log file' as simple as that may sound...

 

Which is why I said at the outset of the claim that making assumption on numbers and calling B.S. is even more pointless.

 

Like I said, unless drivelines have some magical way of putting power into the rear wheel number, Jeff is being conservative in his claims, and I'm too damn busy to framegrab Hi-8 Video frames to suit naysayers.

 

The first post never should have been made terribly rude and sarcastic no matter which way you read it---the second post (if that was the 'real' purpose as stated) is the only one that should have been made in regards to the numbers.

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