For those of you with more experience at reading Dyno's (most of you) I'd like your opinions on the following;

I had my 06 A6 C6 dyno'd in May at a shop after having a twin cone filter intake put on, it was a gift and I was hoping for some induction sound. (nada.)


No baseline Dyno with the stock intake as I was worked into a busy schedule as it was. This is the May Dyno from that install:
335.2/338.9 The first run the car hiccuped when it was punched so I understand the dip.



I thought it seemed about what one would expect with an A6 loss of aprox. 17%?

Took the car to another shop Monday to have coated headers (stainless works), Hiflo Cats (RT), X-Pipe (RT), intake (honker), ported TB, plugs/wires, 160-180 Therm. and a tune. And here is the before and after (finally learned, do a baseline) dyno from this week:



baseline of 308/314?!? Did GM sneak a 6 cylinder into my Vert?

Other thing that baffles me is the funkiness (to me) of the last Dyno. I'm used to seeing Dyno's look like the one from May and I'm just not sure how to interpret this last one, especially the dip in the torque line. The tuner asked if the engine was cold at the other shop and I answered it was, but now that I think about it, the car idled a bit while I spoke to the guy doing the run, and it got better with each run, so it was improving as it warmed up.

Here's the other odd thing. You'd think I'd notice a definite SOTP improvement to the car, and I don't. Granted I've only put 45 miles on her and 75% of that was moderate to heavy traffic so I only got in 3-4 rabbit starts and a couple of 40-75 throttle punches. But I was rather expecting to FEEL a difference. If anything, there seems to be a slight hesitation when I punch it that wasn't there before.

I haven't had the opportunity to speak with the tuner again (they were closing) and I will. Seems like a great guy, has a good rep in the business, and I'm a greenhorn at this so I am NOT complaining here. But I am confused! I'm just hoping for some experienced eyes to comment on the Dyno's and numbers and offer up opinions. I'm thinking of going back to the first shop for another pass on the Dyno to see if the huge difference shows up in the Dyno's again?

 

The raw data you get has lots of noise in it, so the computer smooths out the curve to make it easy to read. Looks like the baseline run just wasn't smoothed out like the final run was.

Also, don't worry about the discrepency between dynos. The idea is not to get an absolute power figure, but to measure the change before and after making changes to the car. Comparing charts from different dynos on different days is meaningless. There are lots of variables including temperature, humidity, dyno model, and dyno calibration that will cause large discrepencies.

 

OK, I'm betting your first pull at the new shop, the car was hot and it pulled timing. You've done similar mods that I have done and this is what I have:

First dyno with just the K&N AirCharger (probably not worth much power increase) I ran a baseline of 334 hp, pretty close to your first pull. Then second pull, car was hotter and it pulled timing and only made 316.

Then I put on LG Long tubes & a 160 stat. Ran back to back runs of 359 then 360 without a tune. So you got another 5 hp with the Honker and the tune. Sounds like you are making good numbers for an auto, but I'm betting the first pull your car was hot.

 

One more thing, you said you didn't notice a SOTP difference. I couldn't believe how fast the car ran when I first ran it with the headers. I still notice it, it's day and night. I did pick up 39 foot pounds of torque with the LG's so I really notice it in the midrange.

 

Did the dyno techs have a sniffer in the exhaust? Seeing the A/F might explain the low rpm dip in tq after mods. If it were a bike,I'd say valve overlap. Maybe EPA lean~ness? ECU modded?

 

Thanks for the responses guys! This gnawed at me last night so I'm going back to the first shop (they're right around the corner from me) for 3 pulls tomorrow. Just darned curious. (BTW, IGNORANCE killed the cat, curiosity was framed!)

Also had ceramic pads and ss lines put on. (I know the lines are considered bling but I'm going to do some Road Atlanta track days and figured WTH) I went out early this morning to bed the new brake pads on the freeway and romped it good getting back up to speed between slow downs. From a roll of around 20 MPH I do notice an improvement. On a couple of WOT's there was some slight hesitation that bugs me, but most of the WOT's were real fun. I still don't feel a difference really from a standstill, but the tuner told me he'd tweak the tune again after I put some miles on it (just under 3K now). So I'll just wait and see.

I also added the Elite SS ceramic tunnel plate. Doesn't seem to me to have done much for the heat but the ride feels a little tighter and I like that.

Thanks again for the input!

Edit: Actually we didn't do the SS lines at this time, was planning on it but ran out of time. Memory isn't what it used to be. Thinking of doing them when I get powder coated calipers. Might do that right before RA.

 

If you're going to RA then I'd take off those ceramic pads. Ceramics are made for the street and do not work well when you really heat them up, which you'll be doing. Also, did you upgrade to dot4 when installing the lines? Dot3 is a no-no for the track.

 

Yeah, the tuner told me he left it a hair rich since the car is low mileage, and that he'd adjust that with a follow up tune, but I can't remember the ratio. Age is relentless on the ole memory. I'll try and remember to ask him when I speak to him again.

 

I did notice during the bedding procedure the brakes started fading fast about the 5th slow down. I was going to do 8 stops but quit after 7 because of that. I'm going to ask them about the fluid, and the orginal pads are still in great shape.

The catch on RA is with a Vert I have to run in C class behind the pace car. Can't run A or B class w/o roll hoops. I'm going to wait and see how much I like doing RA before I even consider hoops, they're pricey and I'm not sure if I'd like the look.

In the back of my mind I'm starting to think about leaving this Vette alone mod wise from this point, and picking up a used coupe next summer to play with.

 

I would make sure you're using dot4 regardless of your run group, unless you're just going to put around. But what's the point of that? I'm not sure of the conditions, but there have been a few C6 owners who tracked their bone stock cars for the first time ever and wound up boiling the dot3. Must have been scary!

 

I don't think you have a problem here. Dynos do not measure absolute numbers, they are only a tuning tool. In any event, you can't compare the two dyno readings because the first one is SAE corrected, while the second one is STD (standard). The only thing that is important is the relative difference, and the second graph seems to indicate you went in the right direction. As long as the engine and dyno bay temperatures were similar when those two pulls shown in the second graph were made, then what you see is what you got. If you compare the first graph (ignoring the absolute numbers) to the baseline curves in the second graph, they look like an almost perfect overlay.

The "after" torque dip is not at all unusual in LSx engines that have improved breathing (i.e., your exhaust and intake work). For example, check my before/after readings in My Corvette Photos at right. In my case, the "before" shows the dip on my LS2 402ci stroker before adding a vacuum pump. It is gone in the "after" chart.

The hesitation you feel may be torque management kicking in more aggressively as a result of your increased low end torque. Ask your tuner to scale it back. Don't eliminate it though - you need it to protect your stock tranny.

Congrats on the good results - enjoy!

 

The first shop's runs looked more correct, and you need to dyno there, to see a true, before and after. Always test on the same dyno, with the same operator.

The dip is no big deal, and is normal. Is your tuner expecting the car to lean out some, or is he adding fuel to desensitize the the tendency for knock? I see some tuners making them rich on a Dynojet, because they know they will run leaner in actual running conditions, under full weight and aerodynamic loads.

 

Here's the Dyno from today at the first shop. Everything is staying in the 360's so the numbers are (fairly) consistent. I noticed today just idling after a run brought temps down to the low 180's with the new therm/ fan settings.




Hex, he's especting it to lean out some, but said we'd check that in 2-3K miles and tweak as needed.

Mr. Lucky, I'm intrigued by the vac pump, 10 points across the board! Would you elaborate on your mods (checked your profile)? I saw what you meant about smoothing out.

When I have the tune tweaked I'll mention the torque management, and point taken. In some 'spirited' testing last night I felt TM come into play more than I usually do. This car is soooo much fun to drive!

Thanks for all the input!

 

Ask the tuner if he turned off the torque management in the computer. After LG did my headers and tune (MN6) it was like day and night.

 

It looks like the guy that did the header install must have screwed up on the first dyno pull. Maybe he put in the wrong inlet temp or maybe the car was hot, but now your numbers are closer to mine as far as what you picked up. You have a better inlet and a tune and it shows.

Before:
yours: 335 hp and 338 foot pounds
mine: 334 hp and 323 foot pounds
(your car made quite a bit more torque than mine did stock, maybe I was getting some timing pullback due to it being 100 outside when I ran)

After:
yours: 369 hp and 363 foot pounds
mine: 360 hp and 362 foot pounds

Increases:
yours: 34 hp and 25 foot pounds
mine: 26 hp and 39 foot pounds

You are making more power and the same torque as my car. The LG's seem to give me more torque with a little less hp on the top, but I think part of the reason you made more power is you are running a better intake plus you got a tune.

I'd be VERY HAPPY if I were you. 369 are great numbers for an A6 with headers and an intake. Plus I think the 160 stat makes the car more consistent.


Great job!
Glenn

 

I was hoping I would see almost exactly what I did see with the last Dyno. Confirmation of what the car is making now, which I am happy with. I'm hoping with the tweaking to be done later I may pick up a just a hair more, or maybe more importantly, have torque management cut back just a bit. From a roll of around 40 mph I think I can actually feel the back end want to come out a bit on WOT, what a beast!

Thanks for the information and opinions. I'm going to discuss much of this with the tuner and would not have known to do so without your input. This place rocks!

 

I'm also interested in more detail about the vacuum pump.

 

Without straying too far OT (I hope), here are a few words about my vacuum pump, for the people that asked.

1) It won't buy you much on a basically stock motor... with the possible exception of a long term investment in the cleanliness of your engine internals. As a horsepower increaser, it is not very cost effective. I did it because I lost vaccum with my cam, plus stroker motors can benefit from the ring sealing assist that the pump offers. The pump (and 2-stage catch can that go with it) completely eliminate the PCV system, so no oil ends up in your intake.

2) If you want further info, here is the original post from A&A. Since my engine pics were taken, I have subsequently upgraded to the "race" pump. Andy doesn't talk this up much or advertise it on his website, but call or PM him if you're interested. Tell him Mr. Lucky sent you (he'll only charge you double ).

 

Good information to know!

 

Without going into all the debate about dynos, on a normal day (about 80 degrees) i dynod 362(see my postunder orange county corvettes) with only the Calloway intake. I will be installing headers in next two weeks and we will se what she does.