Bad News on the Dyno

[DavidH]

After driving a couple of other peoples 944 SPEC cars and Dylan driving mine we suspected something was up (actually, down) and we put it on the dyno today:

 

"Hey David,

just got back from the dyno. Well, I was pretty close! I said I thought

you had about 120 hp, you had 121 hp! Sorry dude, you've been running for

how long now with about 15-18 hp down on many of the top runners? I put the

chip in, that bumped it immediately 5hp across the board. Then I tweaked the

AFM a little and gained another 2+ hp. So, your now at 128hp max. That still

leaves you 6-10 hp down on most of the runners? Also, at 6,200 rpm thru

6,400 rpm, you have a whopping 30+ hp drop! It may be the tracks on your

AFM, something you might want to play with? Anyway, you got some gains, but

you still have a ways to go!!!

 

P.D."

 

 

Help!!!! My car WITH a chip is putting power out that non-chipped cars are. What should I be looking for? I could possibly try a header, or exhaust but should not have to go that route.

 

The only good news is that I have been driving a car that has been down on power and trying to keep up with everyone else.

[944 Swede]

Why shouldn't you have to go the route of headers, exhaust???

Everything matters, it's a spec class.

There is a reason why I have the exhaust and air intake that I have on my car, it increased power.

It's a lot of testing, a lot of money and a lot of time but I would pay attention to Headers, Exhaust, Air intake, Spark plugs, Calibrated injectors, a new AFM (maybe) for starters.

Lots more can be done within the rules...

Do you want to be a front runner or a back packer?

 

Let's see who will be the first to say "Eh, I run a stock exhaust and I'm pretty fast". That line always cracks me up

[Spec-944#70]

Mike is right by testing and tuning you will tweak your way up some more. But 128 RWHP isn't bad!! Just a few details away from the pack. Shoot you'll be kicking my butt unless I get some more driving tips from Jim M!!

[JamesWilson]

We just unpacked our new Dyno Dynamics chassis dynamometer this afternoon, it should be up and running by next week.

 

Weather, machine calibration, machine brand, and many other things can effect horsepower numbers a few percent here and there, but without looking at the graph and type of machine it's hard to tell.

 

Maybe we should plan a 944Spec Dyno Shootout, all run on the same machine during similar weather and conditions? Discouuuuuuuuunts. I'll let Timmy arrange it...........

 

San Diego area.

 

-JW

[944-Spec#94]

Let's see who will be the first to say "Eh, I run a stock exhaust and I'm pretty fast". That line always cracks me up

 

I run a stock exhaust (minus cat of course) and I consider myself pretty fast. I run a stock in take as well. As for spark plugs... bosch copper..

 

David if you look at the dyno charts listed on the 944spec webpage 128 hp is the range of normal.

 

BTW.. To James's Point. Back in 2003 I dynoed my spec car on DynoJet 248 at Technodyne. Car made 131 rwhp. I dynoed the same engine with all the same parts on Dyno Dynamics unit at Dyno Comp at got 134 rwhp. l also look at the area under the curve not just the peak hp. A couple years ago on Eric's motor that lost the headgasket in Phoenix he showed me 138 rwhp dyno chart. Wow that was big power... Well yes and no. My 131 rwhp dyno make more hp till about 5500 rpm where his went up and my flattened a bit. I'd rather have more hp accross the rev range than a few hp up top. Also as for the power drop off over 6000 rpm... That is why I shift at 6000. No power above 6k plus more wear on the rod bearings.

 

 

What is the condition of your head? Has it been cleaned up? (not shaved, but cleaned, flattend and all valves checked for proper(stock) seating? Injectors are also good to check and make sure they are all clean and flowing properly.

[944-Spec#94]

How does the curve compare to these?

 

[944-Spec#94]

[Norman#99]

When I bought my car a little over a year ago, it dynoed at 122 hp at the rear wheels, a few months ago I had the head checked out, to find that it wasn't level from front to rear so I had it shaved to 49k, the valves were also screwed up, so that was fixed. My car is an early 85, so I changed the cam to a later cam which has a little more duration on the exhaust side (87-S cam). Just from that, I am now upto 128hp with 130 torque. With the early brain, it's a pain to chip, so I changed the AFM and Brain to a 87-S AFM and Brain. Now I am needing a chip. Trying to schedule something with the newly married and proffesional racer Dwain Dement. I hope that will get me upto 138hp. Like Mikael W, I am kinda crazy about getting every ounce that I can out of the car. I even put a kill switch on my electric fans to gain 1hp! The cam may have added 1hp or so, but I don't care, I will spend and do what ever legal to get what I can out of the car. It would not be necessary to do all of this if there weren't so many equally fast drivers in this group, so if the drivers are close in driving abilities, then all you can do is get what you can out of your car and continue learning to drive faster. So please let me know what chips, exhaust, driving schools or what ever I can do to get the most out of this spec car and driver!!! I even had my exhaust pipe replaced from the CO2 sensor back with a little bigger in diameter pipe in hopes of some gain. I know you have to watch out for loosing torque when doing that. Let me know when everybody is getting together for a dyno day an I will try to come out for it.

 

Unfortunately I can't race this weekend with you guys, my car is leaking oil around the oil pan so I am having that repaired and changing rod bearings while in there. My good friend and new spec guy Mickey Dowling will be there doing the school and learning the track, so take care of him. Be sure to check his car out, it's one of the best prepared that I have seen!

 

Norman #99

[944-Spec#94]

Just so you guys know.

 

Norm has track the offical track record at PIR and has run pratice laps under the Firebird main track record.

 

Norm is far from slow.

 

 

Norm I would still love to help you with the rod bearings/ oil pan, but I simply cannot get away from the house. With the new baby and multiple trips for work in July and planned in the coming months I would be lucky to have any time for my car. I just hope I can make all the local Az racings.

[Tim Comeau]

Ok, I'll bite, Mikael.................

I was running stock "cast iron" headers and a stock exhaust and muffler and I won a few times.........

I'm still of the mind that we should allow only stock headers, too! The aftermarket headers cost too much money!

[Spec-944#70]

I have stock headers too but I'm slow but I disagree about changing the rule to only allow stock headers. The reason is we have quite a few cars that have spent the money and dyno time to get thier cars to where they are. Just because a few of us are financially challenged (me included) don't make it so they guys who have setup killer cars that meet the rules have to spend $$ to loose HP! This is one of the cheapest classes to run but it is still racing. People will spend money to do whatever they can!! Always will. Even if you made the engines totally stock you would have people buying multiple engines so they could find the lightest matched sets of rods and pistons, and start spending money on headwork to "ensure" they get the absolute most air flow while remaining stock.

Another thing is I do not beleive 5 HP is going to radically change anything. 130 HP will be just as competitive as 135 HP. I would be hard pressed to find anyone who could tell the difference between the 2 motors if they were in the same car. The big gains come from seat time and car setup. My guess is David will be a tad faster but not as much as he would like. After I rebuilt my motor I didn't get any faster and it was only till I had Jim M help pull my head out at CSW that I picked up my times. It's still ALL about seat time and car setup!!

JMHO!!

I know PD is going to talk about HP but only the very best of drivers can squeeze the extra 5 HP out and I'm sure it'll only add 1 or 2 tenths!! At best!!

[944mechanica]

A few comments on your dyno numbers:

 

I'm assuming you've checked cylinder leakdown and that it is less than 10%, preferably less than 5%? The head is fresh as well ?

 

Exhaust manifolds are not cracked or if you run a header there is a good seal at the exhaust ports? This is a tuned system and any exhaust leak at the head will ruin that tuning. Almost every stock header I remove is cracked or repaired. The rest of the exhaust matters as well. Stock 944/924 exhausts, even without the cat are junk. I've seen conclusive and repeated dyno validation that supports this. The 1988 exhaust is probably okay for 944 spec until you start looking for that last 10 HP.

 

The fuel system HAS to be 100%, that is everything from the fuel pump to the AF meter

 

Are you running something other than a stock air cleaner housing drawing air from the fenderwell?

 

Don't expect top numbers unless the engine is fresh and you are running every legal option including a properly programed DME chip. A weak fuel system and a bad chip are worth a 20 hp loss easy. Add in a worn out engine and you can be down 30 hp with a similar loss in torque, which is almost a bigger disadvantage than the HP loss.

[DavidH]

Wow, I have been in meetings all day and look what I came back to...you guys are the best. Thank you for all of the responses.

 

Mikael, my point was that I have been running at 121hp with the stock set up. From what I can tell, that is far short from what a stock motor should be running at. We just put the chip in and tweeked the AFM and now it is at 128. Most are closer to 134 with a chip and higher with the added goodies that you mentioned. I am planning on developing the engine further, but something might be wrong with the motor. Possibly the head as Norm(thanks for the tip Norm) had in his car. It might be a good thing to look into.

 

Eric, seat time is what it is about but having a strong & well set up car doesn't hurt. Heck, knowing that I have been running a 121hp car makes me feel better about my times. I know the driver of my car needs more developement than the car, but the car can be fixed I should probably be fixed as I have enough kids I am working on the seat time and will continue that.

 

Tim, you have just a wee bit more experience than I do and can probably run just about as fast with a 121hp car as with a 138hp car...just about...

 

I am happy that the car is closer in power now, but would like to get more out of it. Maybe not today, but in the near future. That is part of the fun.

[DavidH]

Norm,

Thanks for the dyno numbers. Actually, the first place I looked to get some numbers to compare to was your SPEC944 site. I just didn't see anyone close to 121hp (that is where I started). As P.D. mentioned, I have this weird (and huge 30hp) dip at about 6200rpm. Maybe the AFM.

 

Steve,

Your list makes perfect sense and I will probably (over time) use it as a check list. I am running a K&N filter in the stock housing. The engine is anything but fresh (130k miles), but did a leakdown and compression test and it checked out OK. I will have to pull the paperwork from my files to get the exact numbers. The only thing that I did was rod bearings a year ago to help prevent anything catastrophic from happening.

 

Here are some comments from Mr. P.D.:

 

"David if you look at the dyno charts listed on the 944spec webpage 128 hp

is the range of normal."

 

I see a couple 'below' 130, and most 'above' 134 hp. What is also missing

from that chart is many of the guys with the big numbers, above 135 hp. And

the fact is, as Mikael says, every little bit does help. Why would everybody

chase it otherwise? It may not be usable to everybody, but it still helps.

Fact is, not one person with 134+ hp would swap engines with David to prove

it 'doesn't really matter'. I 'clearly' felt the difference between David's

car running at 121 hp and mine when it ran at 125 hp. And let me share, a

10-12 hp difference on a 2nd gear corner to 5th gear end of straight run,

was worth about 4-5 car lengths by the end of the straight, consistently in

my last race at Vegas. Is a spec series, 4-5 car lengths is tough to make up

everywhere else. And just because you don't see that big a loss on other

parts of the track, it obviously still occurs. Of course the net result also

depends on how well you corner or brake, I'm not arguing that fact. Assuming

you and the other driver corner and brake the same, you will continue to

lose ground all the time if you have less hp (not considering radical curve

differences as Joe mentioned).

 

"Also as for the power drop off over 6000 rpm... That is why I shift at

6000. No power above 6k plus more wear on the rod bearings."

 

I used to do this practice at Willow, based on the same advice that there

was a drop off in power above 6K. Then one day in a single session I did a

comparison test. I switched back and forth between 6K and 6.5K shifts

heading towards turn 9. The result was, shifting at 6.5K resulted (every

single time) in an extra 5 mph at the slow down point for 9. So, why would

you want to shift at 6K just because the power drops off? Especially if the

power at 6,500 is higher than the power at 4,800 or so where the revs drop

to when you shift at 6K? Sorry guys (Joe and Tim), I just don't buy into

this shifting at 6K because there is no power beyond that point.

 

P.D.