May Car and Driver issue

[paul e]

Two Interesting articles... First, rms blows their S62 v8 M5 for a ridiculous cost, and with a somewhat lesser result than the Dinan na S2M5.

But the more interesting article is how todays cars are too intellegent for our chassis dynos.. And the expert they use is none other than Steve Dinan. Heres the example:

Dinan bolts to his dynopak one of his M5s, heavily tweaked to produce a claimed 470 crank hp, and 415 claimed whp.. which sounds like a 12% drivetrain loss.. a little low, dont you think? Ok, anyway first run with the hood closed, and the car makes 334whp. Datalogger shows that because of the high engine heat, afr has plummeted to a crazy 9.5:1. Next pass, is with a regular home depot type fan like most dynos have, and the car makes 371whp. Finally, Dinan brings out the big guns: a $7000 turbine fan that blasts 38000 cubic ft per minute at 75mph down a narrow duct!! And as a result, the car spits out 412 whp!!

So, does this mean that All our results , done with the homedepot type of inadequate fan, are at least 10% less than they would have been, were we using Dinans humongous turbine fan?

Point of the article is that unless our dynos catch up to the modern' cars computer abilities, we'll just keep getting farther and farther from anything resembling accuracy. Kind of interesting article for car and driver..

And, for my money, points to the fact that to use a dyno for anything besides before and after mod checks is completely superfluous.

Maybe wed all be better off using that 'home dyno' tool and software, because at least IT takes its readings, at speed, with good airflow, on the street :)

[Mitch P.]

I'm with you Paul. Awesome article which confirmed what many of us have known all along. Baseline first, mod next, then re-dyno.

Luckily, most of us have gotten pretty close to what Dinan (for ex.) has claimed. It always made me crack up when someone started crying wolf when their dyno session returned 10hp less etc etc. It all depends on the conditions.

I was also less than impressed with the RMS SC'd M5. I started shaking my head when I read the CEL's were illuminating, and driveability. Not something you want in a magazine as widely read as C&D IMO.

[paul e]

>>I was also less than impressed with the RMS SC'd M5. I started shaking my head when I read the CEL's were illuminating, and driveability. Not something you want in a magazine as widely read as C&D IMO.<<

I know.....lol. Youd think that at least for Car and Driver theyd have gotten it right, you know?! That was perty funny... :)

[Mitch P.]

I'm guessing people who have enough money to buy an M5 would have been rolling their eyes? Anyhow, I sure was less than impressed.

Now the dyno article sure was interesting. Not that it was new information, but the fact that I don't think I've ever seen a C&D article go into that much detail with regards to anything except factory hot rodding. Do you think the article was driven by staff or by Dinan?

[themadhatter]

it's not on their site, can anyone scan the article for me?

...and yes I subscribe to C&D but I'm in Africa. C&D is kinda hard to come by here. :(

[WebDev]

After the various words exchanged on this forum about the RMS quality level it doesn't make me feel any better about them to hear that the CEL was lit and they still needed a little more software tweaking to get the car to drive right and perform better than the Dinan M5. Way to softball that one C&D. Just come out and say it, for $25,000 (what? gimme a break!) you can get yourself a kit that might work or maybe it won't. Maybe it will make 600HP or maybe that is with a little more software tweaking.

[M3TurboCa]

Definately not what you want in publicity for RMS. Only they would know why they release the car to Car & Driver in that state unless they were pressed for time.

Paul I mentioned to you before asking you the a/f that you see on the road under wot compared to the dyno what differences do you see. There should be a difference as the air is more dense and colder on the street.

I know that a friend that tunes the cars on the dyno makes them .5 to 1.0 richer compared to using a wideband on the street it will tend to lean out a bit.

Maybe on your dyno day on Sunday you can log on the street and on the dyno to verify any changes.

Damm dyno company's should have guide lines about have a few high flow cfm fans that meet a certain requirements.

Two on the front and one blowing on the engine. :)

[zenon]

looking for C&D to read this article there were unfortunately only april one's in:(

however while browsing the rack I found the may ed of HOT ROD has a 6 page article devoted to dyno's, well worth the few dollars for one issue IMO.....FYI.


waiting for the may C&D to arrive...........

[paul e]

>>Paul I mentioned to you before asking you the a/f that you see on the road under wot compared to the dyno what differences do you see. There should be a difference as the air is more dense and colder on the street<<

Ahhh.. Great Question! There IS a difference, but not because the air is any colder or denser on the street.. I took a dyno run on Jan. 20 in the middle of our really cold snap, and the air was in the upper teens at midday. But, hey, I was in the middle of tuning, so I wasnt going to let a little thing like THAT discourage me! In the dyno room, the temp registered 40 degrees, but as soon as we were ready to make a pull, up came the doors in front and back of the car in the dyno bay, and the fan was set a spinning, and that sub 20 degree F air was funneled right into the cars engine bay and intake. And what happened was that One ecu that had recorded 312 rwhp when it was near 50 degrees, pulled a 330!!! ON the fourth run of the day too!

But as for street AFRs taken Pre catwith the wideband vs Dyno AFRs taken Post cat in the tailpipe, the main difference is that up til maybe 5k rpms or so, the Post cat AFR is leaner. Thats because it takes til about that rpm level before the air in the cats is Purged sufficiently to get a true reading. But even up top, the pre cat reading was slightly richer. If youre tuning, and want good readings, Id say there is a big enough difference when taking pre cat measurements to make a difference in your final tuning.

[///M3DarkSide]

Dinan has a few articles on their website, (www.Dinancars.com) one of which is about how to accurately use a dyno. In fact I bet the articles are quite similar. As for the gigantic fan that they use; I would almost consider that cheating. Obviously most shops wont have that sort of fan and actual manufacturing plants have no need for a fan or anything because they measure actual crank hp. The point is although the readings are more consistantly accurate with the setup that they use (ramming air into the engine,) all of their hp ratings are going to be significantly higher than anyone elses, not too mention simply unachievable during real-world conditions.

[Mitch P.]

cheating? When you are doing a 4th or 5th gear pull, the engine needs the equivalent of that much air passing by it. That means 120mph+ equivalent. So it's not cheating at all, it's more in tune with what you'll see on the street. Cheating is putting ice packs on the intercooler...

[paul e]

Following is a short excerpt of something my Dyno owner sent me re this whole business:

"I did the math.

In order to get 38000 cfm to go 75 mph, one needs to have an opening of 5.76 square feet. Make the opening any smaller (a "narrow duct" like they said) and either the speed goes up or the cfm goes down. If they actually did hook such a powerful blower up to a narrow duct and aimed it at the intake, they created a form of forced induction. Otherwise, there is simply no way a fan blowing across the engine compartment added 80 hp. 75 mph on the highway with a closed hood is not going to keep things much cooler. I would seriously question those numbers if I were you."

[zenon]

"ramming" effect's are negligble, no measureable change in hp will occur @ legal north american speeds.

cool fresh air however, very beneficial.

[///M3DarkSide]

cheating? When you are doing a 4th or 5th gear pull, the engine needs the equivalent of that much air passing by it. That means 120mph+ equivalent. So it's not cheating at all, it's more in tune with what you'll see on the street. Cheating is putting ice packs on the intercooler...

What about 1st, 2nd and 3rd gear pulls? That is where you need the power if you are doing 0-60 or quarter mile runs and in those gears you wouldn't have that kind of airflow.
A true engine dyno would use only ambient air pressure for testing. An engine is, in essence, an air pump. It PULLS air in and the pushes air out. Forcing the air into it (via a 2nd machine) defeats the purpose and will without a doubt directly contribute to an inaccurate hp rating.
Look at most dyno-graphs: Y-axis = Horse Power; X-axis = rpm. Speed isn't a factor.

[///M3DarkSide]

"ramming" effect's are negligble, no measureable change in hp will occur @ legal north american speeds.

cool fresh air however, very beneficial.

Ram Air has been used for years, especially on cars from the 60's and 70's. I believe the GTO's and Firebirds had ram-air hoods that could be activated at speed for a small (yet noticable) increase in power.

[///3oris]

What about 1st, 2nd and 3rd gear pulls? That is where you need the power if you are doing 0-60 or quarter mile runs and in those gears you wouldn't have that kind of airflow.
A true engine dyno would use only ambient air pressure for testing. An engine is, in essence, an air pump. It PULLS air in and the pushes air out. Forcing the air into it (via a 2nd machine) defeats the purpose and will without a doubt directly contribute to an inaccurate hp rating.
Look at most dyno-graphs: Y-axis = Horse Power; X-axis = rpm. Speed isn't a factor.

Some put SPEED on the X-axis :devillook:devillook:stickoutt

Boris

[zenon]

I'm actually a big muscle car fan myself.

Ramming scoops prevent buffeting on carbureted motors and provide cold air, buffeting is a non-issue on fuel injected motors. The benefits of cold air however are still very applicable.


The ramming effect of a car traveling @ 90MPH will result in a 1% improvement in power, at 150MPH this will rise to a staggering 2.75% improvement.

At 75 MPH the improvement is roughly 0.8%..... Period.
Whether that's 75 MPH on the open road, 75MPH in a PVC pipe or 75 MPH in a wind tunnel the improvement in power will be 0.8%.

The fan's ramming air effect is non-existent on the dyno.



interestingly it's the guys with speed on the bottom that are using "real" dyno's..... even if the plots are cumbersome to read :eyecrazy:

[NickG]

You guys only seem to be focusing on the amount of airflow the fan can produce, and if it creates some sort of ram air effect. Don't forget that on recent ECU systems, temps (both air and coolant) play a huge role in the engine's power output. The ECU, in an effort to save the engine, can pull out drastic amounts of spark timing with increased air and coolant temps. The mixture can also be richened substantially. All of these things are to keep the engine alive and reliable, and can greatly affect power output. I wouldn't doubt that it could make over a 50hp difference on a 400hp engine.

[paul e]

>>The ECU, in an effort to save the engine, can pull out drastic amounts of spark timing with increased air and coolant temps. The mixture can also be richened substantially<<

Thats exactly what it said in the Dinan part of the cAr and driver article..."...Datalogger shows that because of the high engine heat, afr has plummeted to a crazy 9.5:1. ..." :)

[Mitch P.]

What about 1st, 2nd and 3rd gear pulls? That is where you need the power if you are doing 0-60 or quarter mile runs and in those gears you wouldn't have that kind of airflow.
A true engine dyno would use only ambient air pressure for testing. An engine is, in essence, an air pump. It PULLS air in and the pushes air out. Forcing the air into it (via a 2nd machine) defeats the purpose and will without a doubt directly contribute to an inaccurate hp rating.
Look at most dyno-graphs: Y-axis = Horse Power; X-axis = rpm. Speed isn't a factor.

I think you missed the point of the article as well as what I was trying to say. In order to have the best possible attempt at a best approximation dyno run, we all run in the direct drive ratio (1:1 = 5th gear on an E36M3) or damn near that gear if the dyno operator doesn't want his drum spun to 160mph. Thus the dyno in 4rd gear in an attempt to take out as much driveline losses as possible. The fact that the engine is pulling a load equivalent to 130mph, the ECU will want to see the equivalent cooling at that speed. Thus the airflow required to keep the coolant and oil temps down. Otherwise, as Nick stated (as well as the article), today's smarter ECU's will pull the timing (thus hp/tq) in order to protect the engine.

No one does a 1st, 2nd, or 3rd gear dyno pull as many of our high hp/tq cars will induce wheel-spin and you are fighting additional driveline losses anyways in those lower gears.

Ram-air? C'mon. Ram-air is a marketing term in the automotive world. As Zenon and I in the past have pointed out, there's no such thing as a ram-air effect at anything lower than close to supersonic speeds. That fan had nothing to do with forcing more air into the engine. It was merely there to produce an approximate airflow through the radiator and around the engine in order to keep the temps down as that's one hell of a load on an engine to spin the roller (which is very close to a real world run without the air resistance) up to 130+mph.

[Mitch P.]

one more point I forgot. When you referred to 1st,2nd, and 3rd gear real world pulls, the engine is not under as great a load as it would be in 4th and 5th gear. The higher the speed, the higher the load as aerodynamics play an effect. Try this: put your hand out the window at 35mph (redline in 1st gear) - now how much aerodynamic drag is being produced on your hand if it is in the stop position? Not much right? 2nd gear redline = 60mph is a bit more right? Third gear 95mph the drag is pretty damned high. Try that in 4th gear and you'll rip your arm off! Same thing the engine sees - at 130mph it's a huge drag/load on the engine and increased cooling is needed.

[///M3DarkSide]

Some put SPEED on the X-axis :devillook:devillook:stickoutt

Boris

True, but if speed is on the X-axis then rpm is not. And if you look REAL close, you'll notice that the graph is different. ;)


You guys only seem to be focusing on the amount of airflow the fan can produce, and if it creates some sort of ram air effect. Don't forget that on recent ECU systems, temps (both air and coolant) play a huge role in the engine's power output. The ECU, in an effort to save the engine, can pull out drastic amounts of spark timing with increased air and coolant temps. The mixture can also be richened substantially. All of these things are to keep the engine alive and reliable, and can greatly affect power output. I wouldn't doubt that it could make over a 50hp difference on a 400hp engine.

I knew I could rely on someone like you to talk about the cooling effects. After all, it is very important. I was going to bring that up in my other post, but I thought I would probably just end up rambling. Cooling is definitely a very important factor and that is a very real reason to have such a large fan, but that doesn't negate the power increases that it will consiquently produce. Negligible or not it contributes to an inaccurate reading.
However, let me say that I understand that, short of pulling the engine out, there isn't a 100% accurate dynometer and the way that Dinan goes about it will provide CONSISTENCY even if the numbers are a little higher than reality.

[Alex McHenry]

50hp difference? Maybe.. according to Dinan at least. You'd be better off expressing that as a percentage, and yes it can be calculated based on various factors like air temperature, humidity, etc. However, a big ass fan in front of the car isnt' ramming anything anymore than driving your car down the road is..

[MGregski]

Back to the article - what it forgot to mention is that the engine blew up during the Car and Driver test!!!:D Go to the M5board, or check one of the links here concerning RMS.

[paul e]

>>Back to the article - what it forgot to mention is that the engine blew up during the Car and Driver test!!!<<

Blew Up? C&D simply said it flagged a CEL, and went into Limp Home mode, which isnt good when youre testing for power but its a far cry from blowing up :) Perhaps C&D didnt tell us the whole story..

[DocWyte]

Wouldn't be the first time a magazine didn't tell the whole truth concerning a tuner car...

[MGregski]

That is the truth, from what I've heard is that it threw a rod.:confused: