Frost

iTrader: (45)

Hey guys have a question or so for ya...

I tune on a local dynojet 224x. The dyno I use does not have the eddy current brake option, so i usually do VE tuning on the street (MOST of my tuning is actually done on the street) and just finish the cars up on the rollers. For NA cars and SC'd cars this works great. HOWEVER... I cannot tune WOT for turbo charged cars ont his dyno at all. As a matter of fact, it doesn't even load up the cars enough to get any type of realistic spooling. I will use my own car as an example... I have a 76mm (P76GTS) front mounted turbo and make 16-17psi on the street FAST in fourth gear (3K-3500 RPMs I'd say) but on this dyno, I cannot make more than about 10psi Obviously I don't want to tune my car on it, but I can't even get numbers out of it. I hav seen an STS car that I didn't tune do the same on it.

Now... obviously the eddy current add-on would be nice, but that isn't going to happen at the place I use. Recently though, another local shop is looking at putting in a dyno and is talking with me about doing their GM work and asked me what I thought about the 248x. I have had my car on a 248 in the past and it had no trouble getting my car spooled and up into boost. I am still concerned about the accuracy of the loading though, which brings me to the central question of this post. For those of you tuning on 248s, when yout tune your WOT for TURBOCHARGED cars on the dyno, does the same final AFR carry over to the street?

Thanks for your time guys.

edcmat-l1

iTrader: (10)

If you load em good, it will be within a .1 or so to actual A/F on the street. If they get a 248, make sure they get the proportional air brake kit. It lets you apply the dyno brakes for added load. There some other tricks to using these inertia dynos too. Call me if ya get a sec.

NicD

iTrader: (7)

The only turbo cars that I have had a problem loading properly on a dynojet without a brake control setup are the STS vehicles. All of the traditionally mounted front turbo setups do seem to spool slightly slower on the rollers but they still make the correct boost. For the turbo cars that duplicate the same boost level on the street as the dynojet it's pretty much identical a/f wise.

One trick I use for STS vehicles is to run it around 3500 rpm on the rollers for a minute or two cruising and slowly accelerating to get the turbo nice and hot and then do your standard pull. It's usually good for another psi or two on a non-loaded dynojet and get's you closer to a street/track pull.

Frost

iTrader: (45)

Ed, thanks for taking a minute away from your busy day for me on the phone



Hey Nic, thanks for your input here... which one do you use, the 224 or 248? Like I mentioned above, I know that my car will spool just fine on a 248, is that the one that you use primarily? Or did you mean that most front mounted (like yours) will spool fine for you on a 224? As far as AFR is concerned, I guess what I was really asking is does the boost made there carry over to street loading pretty closely?

I have *never* tuned a turbocharged setup on a dyno, as I said, all I had available was the 224. I think those rollers sim a like a 2000lb load.

Alvin

iTrader: (2)

Has either shop considered a 224xlc? Thats what I have and love it. Some cars will not have an issue with loading however some (like STS I have found also) will. For this the loading dyno is really handy. It is also nice to slow down some of the big power cars so you can really see what is happening.

Also, another interesting note. I have not seen a GM yet change AFR between a loaded pull and a unloaded pull. I have notice that Ford cars do change AFR quite a bit when loaded. Its never predictable. Some go rich while others go lean.

Frost

iTrader: (45)

Tuning on a 224 unloaded and going to the street for non-turbo cars seems fine, and I always check things. IF there is ever a difference, it's only a tenth of a point or two in AFR. And as is always noted, more timing can be run on the 224 unloaded than the street.

Thanks for the info guys.

Bullitt4110

iTrader: (31)

I dont know much details about it, but I work for a tuner/ dyno shop. Our dyno is the 248 and I am pretty sure he just uses the brake to load up the turbo cars, and he has done quite a few so I am pretty sure that works well.

NicD

iTrader: (7)

All of the turbo cars I have done have been on 248s. The A/F made on a dynojet always carries over fine on the street as long as the boost is consistant. But like I said the only cars I have seen that aren't consistant are the rear mount cars even on the bigger 248. My trick of getting the turbo nice and hot before the pull gets that extra PSI or two out of it and keeps it pretty damn similiar to the street. When I see people post up that their car runs a half a point leaner on the street than on the dyno it tells me they are well past the MAF and end up running more boost on the street for some reason or they are hitting cells in their 2/3 bar tune that they couldn't hit on the rollers. I guess it could also be just them repeating something they heard on the internet. I just keep most attention on the timing as you most definately can run more timing on the rollers than on the street.

qqwqeqwrqwqtq

Yes. When I tune a BS3 equipped car in open loop, then turn on the wideband at the track I usually have 0-2% correction, the air/fuel being nearly identical to what it was on the dyno.

No dyno will be a perfect example of what will happen on the street/track but you should be able to get damn close.

Frost

iTrader: (45)

Thanks guys, this really puts my mind at rest. I appreciate the input.

If anyone else has anything further to add, I'm all ears as well.

dan@masportspeedshop

iTrader: (6)

If you'll allow me to add...

Turbos rely on load to spool up. They spool up on heat energy, and that is directly proportional to the load that you put on vehicle. If the rollers weigh x and the car y, you will have different loading and while you can get the tune very close as is mentioned above, the question (and worry for the shop owner and tuner) is whether the car will be fully tuned for what it sees in the streets. We use a Mustang dyno and can load cars up far past what they can achieve in the streets, thus allowing us to tune the complete range. We have yet to see a car come back with any problems. If you can't fully load the car, you can get close to an ideal tune at the loads that you hit while on the dyno, but do you really want to risk guessing with the tune beyond those loads? And the street is no place to load a car in 4th gear at 16 psi (sorry for the nanny remark)! I certainly don't want to pay warranty money out for stuff like this, so instead we just bought a better dyno to begin with. What I'm saying is that if the shop you deal with can't pony up for a load cell dyno, at least make sure that they can upgrade later. If anyone is serious about tuning performance and making sure the customer cars stay safe, durable and reliable, you simply have no choice. You must buy adequate equipment. I'm not trying to burst any bubbles here or step on any toes, just point out a simple and long standing reality.

Ryne @ CMS

iTrader: (10)

i have always had trouble tuning turbo cars on a dynojet for the exact reason frost said above (i was using a dynojet 224) thats why when the time came around for me to buy a dyno i bought a Dyno dynamics dyno, i can load that thing til it stalls the car if i want

mahhddgtp

You guys have the 248x at Speed Inc, does that load up enough? You said you have about 0-2% correction, so I'd assume so.

Tom@SpeedInc

iTrader: (5)

My car spun the tires on the dyno, nitto radials. if their was 0 load that would not happen.

I don't think Jim has issues, i've asked him if we should get an eddy dyno, not intersted.

edcmat-l1

iTrader: (10)

Agreed. The 248 drums are a pretty good amount of load.
You guys at Speed Inc have the proportional air control?