IcemanG17

In order for the 928 Estate to qualify for NASA GTS2 class it needs to make a power-weight of 14.5hp/lb The empty weight of the Estate is 2794lbs...I am right at 200lbs with my gear....so my off track weight should be around 3050lbs or maybe a bit less if its super empty.... weight is the weight of car plus driver as it comes off track after a race!

The HP formula for engines that make more torque than HP (like mine does) takes both the HP and torque added together divided by 2....so my last dyno run of 203whp-241 torque ends up with a "power" number of 222...which means I would have to ballast up to 3219lbs to make "class".....the thought of adding a small passenger to the Estate doesn't sound good to me...so I need to bring the HP & torque down....

I can live with a "power" number of 210.....so say 190whp-230 torque will work....I do think my 203 run was a bit on the high side....high 190's to 200 seem more normal....

Okay so ideas......I think I could take a couple degrees of timing out...since I have it set 2' advanced from spec....currently its 22' at 3000rpm and spec is 20' at 3000rpm....I think that alone should do it.....

Intake restrictor is another idea....I could make a box that fits over the air horn inside the airbox (under filter) with a slot for quick change restrictor sizes out of plastic......

Other ideas???

Speedtoys

Add weight and detune..do some of each.

Then you get to pick where to add it, and that can be an advantage more than a disadvantage sometimes.

Tune whatever you do for a cold day. If you didnt, and you got one...ive seen people DQ on the dyno because of weather, same as with sound on a cold overcast day -vs- warm clear day.

atb

Less torque? You could drive a 911.

You could put in a restriction that would keep the flapper door from opening fully. That would seem to be a good way to keep fuel metering in check as well?

danglerb

Why not go to something other than a Dynojet?

hacker-pschorr

Turning the timing down is quick, easy, and repeatable. I would go back to wherever you do your tuning, or better yet at the track and do multiple runs at stock one or two below and one or two above. I would also mark in the distributor where each setting is. I did this with my 81, and each time I adjusted it back to one of my marks it was dead on.

NASA brings a dyno to the track.
Do you honestly think they just look at the dyno sheet and say: "Ok, you pass"..?

If it were that easy he could go to a Mustang dyno and change the drum weight. Want to see a sock Miata make 1,000rwhp?

Speedtoys

Its lined out in the GTS rules:

..all compliance runs at events will be made on a Dynojet Model 248, 224, or 424 in SAE mode with a smoothing factor of 4 so it is highly recommended to use one of those dynos with those settings for certification to avoid any errors in classification.

To allow a small safety margin for dyno variance, a forgiveness of 4WHP will be given to cars with WHP greater than WTQ and a -4 factor will be applied to the formula for cars using the averaging method for WTQ greater than WHP. However, if a car does not meet the minimum weight listed on the certification sheet, the forgiveness cannot be used to arrive at a compliant number.


Its what is most commonly available AT the track events...pretty much.

danglerb

Ah, gotcha, well then has the Estate been run on a compliant dyno with those settings?

IcemanG17

Yes the official dyno for NASA norcal no less.....MCE at Thunderhill on thier dynjet...here is the offical dyno run of 3 pulls, using the highest of the 3....

These runs were in 104+ heat with the timing set advanced.....here is the dyno

Another idea is to go to a LARGER exhaust......since the exhaust is pretty restictive now.....its 85-6 headers into a single 2.5" pipe replacing the cats then into the stock intermediate muffler section and a single maganflow out back....so its not ideal......a higher flowing exhaust should bring peak HP up and torque down....might not be a bad thing?

dr bob

Brian. Adjust the throttle so it doesn't go full open. That will keep the low-mid torque but limit the max power.

danglerb

I'm thinking something that would raise the lower end of the torque curve while reducing the peak might be ideal. A wider, flatter curve, with less peak.

Fabio421

Theres an idea. Put a rock under the gas pedal. Remove the rock for the big race. Smoky Yunick would be proud. LOL

hacker-pschorr

Funny you should say that. It wouldn't be the first time someone was caught with a hidden switch that changed the boost and / or ignition timing once off the dyno.

Do what some pro's do, on the last lap drive through all the debris on the outside of the track to pick up some extra weight

mark kibort

I said it before. just put a more restrictive air filter. us a KN paper filter, and if that is used already, put a tee shirt over it, or try different cloth densities. I just lost a big race, due to my filter being clogged up with laguna sand. It made a big difference at the track and changed my shift points down the main straight by near 50 yard longer!

as far as wide open exhaust, thats an other wives tail. I did this and have the dyno for YOUR cars set up. every exhaust change from headers to 3.5 "pipe, shifted the entire curve up. the only thing that changed the HP curve was timing, albeit only a few hp. advancing the timing gave more torque and less HP by about 4, but we are only talkng about a 4-5 degree change . you might want to retard the timing a lot and see how that changes the hp output and MARK the disti to have it repeatable, as was said before here.

mark kibort

dont worry so much about the ballast weight. you can make your car plenty fast by sticking larger rims and tires on it. do my fender pull out technique, get some 10s front and rear and run 305s all the way around. remember, the audi team in WCGT, ran 275lbs of ballast weight and won at road america with a 2:14, a full 5 seconds faster than anderson has ever driven his beast to! Point is, if the car is set up right and has big tires, it will brake and corner like a dream, just look at what nascar can do at 3500lbs!

anonymousagain

+1 for addressing it via ballast weight. You're accustomed to the power output, so while you will have to adjust to it happening "slower" due to the added weight, at least you let the engine to what it already knows how to do and provide the power delivery as you are familiar with.

Remember you'll have to address driving it differently either way, so stick with the easy adder of weight instead of monkeying with how the engine wants to run...plus it's far more controllable/repeatable to make class.

Mark's "305's all around" suggestion would be a blast !!