Hey guys. This is my first post so bare with me. I have a bone stock 2005 C6 vert with the M6 - non z-51 package. I ran the 1/8 mile and it only hit 78 mph on every run, so that indicated it was not running very well. I know you will ask so.....the 60 ft was anywhere between 2.1 - 2.3 and the times were 9.1-9.2. I know the 60 ft. is hurting the time, but it should not be killing the mph.

Long story short , I took it to get a baseline dyno to see if that gave me any additional information. Since I don't have 'rights' to post pictures here, I did post the dyno jpeg in my picture gallery for those of you who want to look at it. The did the SAE smoothing of 5 and it is still choppy. Also it indicated an SAE corrected 324 rwhp. The first run was 210, but they let it cool and ended with 324. From what I read that is low for a manual. The car drives fine and does not have any codes. It does have 65K on it. The dyno operator said he thought it was detonating and said to check the plugs.

Any opinions on this? I am planning on changing plugs but wanted to know if there was anything else that could make this happen.

 

That's not really THAT low. LS2 makes 400 hp at the crank, and you get about 15% loss to the wheels with a manual which would be 340 rwhp ideally. For a nearly 7 year old car that is still stock, to lose 16 hp isn't really bad.

 

I agree. MN6 LS2 should be between 330-340 at the wheels. If you put it on the dyno, the tuner should be able to tell you if you had any detonation. Did you see any mid run puffs of smoke from the tailpipe? Thats a good indication that the motor saw detonation and the ECU pulled timing. Also, at 65k, changing plugs certainly wouldn't hurt.

What evelation or DA were you at that night? My stock MN6 ran 8.8 at 86 mph with a 2.1 60' spinning through the first 2 gears. I don't consider myself a good drag trip driver, but I have heard some guys running low 8.1-8.2's in the 1/8th with stock or lightly modded cars.

 

Take a look at the dyno chart in my albums. It is really choppy for SAE smoothing of 5. The tuner did say it was detonating, but that seems to be a guess based on what the graph looks like. It is definately not running as smooth as it should per the graph.

Taken 19 - - you ran 86mph and I was running 78 mph. Big difference on power. My guess is it was pulling timing like crazy. Track elevation is only 253 ft.

 

That does look a bit choppy, but I think my header only graph was similar. I will post your graph and mine when I get home.

Couple questions - why is torque not included on graph? Why is speed posted and not engine RPM? What gear were you in? 4th gear run will post most accurate data. The graph only runs to about 137 mph. With a non Z51, your 4th gear should run out to about 160. At 137, your engine speed is 5500 RPM or less? That would easily explain low numbers. Stock vette peaks at about 5900 RPM.

Did tuner have laptop hooked up? If so, he could tell you exactly what RPM timing was being pulled and how much. May be a good starting point.

As far as the strip, what were your shift points? My old 350Z would cross the 1/8th at 81-82, and it only had about 310 up in the motor. Something definitely seems off.

 

Unfortunately, my dad took it to the dyno shop so I got my info second hand as well as talking to the guy on the phone a couple days later. I know from the graphs I see with SAE smoothing of 5 it is choppy. He forgot to give Dad the torque curve, but I can tell you he took it to 6000 rpm in 4th gear. It is an extremely reputable corvette shop here in Raleigh so I trust him when he says something was a little off.

As far as the strip, I was shifting around 6400.

I am going to change the plugs and run out the current gas. I guess the only way to know for sure what is going on is to let them datalog it and see what is happening.

 

Could be detonation related. Try new colder plugs (NGK TR6, for example) and add some Lucas Octane Booster to the next fillup; then do another pull and see if anything changes.

 

Damn. Something's wrong. My bone stock SS trailblazer runs 9.3's in the 1/8th all day.

 

Here's my 1st dyno graph. It's the before and after with ported throttle body, ported intake and headers. The pre-tune is choppy just like yours, but the tuner managed to smooth the graph out after some adjustments.



Here's your dyno:

 

Thanks for getting my graph posted. Wow your car made some good power stock.

I know the dynojet can smooth out the chart up to 5. I am not sure about the smoothing number capability of the mustang dyno. All I know is that the dynojet with a 5 smoothing is usually very smooth. That tells me I was all over the board.

 

Yes, I am for sure changing the plugs. The shop told me to go with the TR55's. Hopefully when I take out the plugs they will show some some signs of being bad. I am sure the stock plugs are in it.

 

That wasn't stock, it was before and after tune with headers, ported intake and ported TB. The graph was SAE, smoothing 5 on the Mustang. I put it on a local Dynojet and it made about 20 rwhp higher but virtually the same torque.

Now that I have been to the dyno 4 times, the curve is extremely smooth (with ported 243 heads, cam and FAST 102), but that is after about 10 hours of collective tuning. If your car has never had a tune, the combo of stock tune and some detonation could explain what you are seeing.

 

Knock retard. Seen it a hundred times at least. I can post graph after graph of it, before and after tuning.

 

Here's a post I made on another forum about a year and a half ago.........

Just a quick run down of what KR looks like on a dyno graph, just so the uninformed know what to look for when they go get their cars dynoed/tuned.

First off, KR is never smooth. It is abrupt. If the engine is out of it's happy zone, as far as spark lead, the graph will be very rough. Here are just a few examples of KR, some of them with before and after results. The after results being either softening the knock sensors, and/or reducing the timing to get the motor happy.

Notice the obvious step at 4100. All the following graphs will have this noticeable step. Some worse than others. Another thing to note, especially in the before and after graphs, is the smoothness after. Notice how choppy this graph is.


Knock retard @ 4900, before and after. Notice it not only doesn't have the step, but is now smoother right after the point where it previously knocked.


Here's one with a more drastic difference. Motor still didn't look totally happy though. Still a rougher graph than I like to see. KR @ 3250, there abouts.....



KR before and after, 3750 rpm......


Here is a more drastic one, but a good example of the gains from just getting KR under control, and fueling too.


Here's one that pulled twice. Double whammy. 3700, and then again at 4700. Notice the graph overall is smoother after getting rid of the KR.


I hope this helps some of you out there understand what knock retard looks like. So when you go get your car dynoed, you'll know what to look for. If it helps one person, I've done my job here.

Again, to summerize, knock retard is never smooth. It doesn't come in smooth, it doesn't recover smooth. The OP's graph that has 2 dips, is most normally caused by a combination of cam profile, and intake/header tuning. I've had cars that had dips in the graph, only to loose them by running open header, or by switching to a different length primary tube header. Sometimes these dips can be lessened by tuning the timing tables, but if you get to a point of having a flat timing table, where they would normally have a timing dip around peak VE, there's not much else you can do.

 

Wow....looks like you nailed it. Looks like mine is showing up around 3700 - 4000 and never clears up. That would also explain why the rwhp never recovers and reaches where it should.

What are my options to fix this? As I already stated...this thing is bone stock with an extended warranty so I cannot get a tune until the warranty is done. I always run 93 octane so I am a little perplexed.

 

Just needs a tune I believe.

These cars come this way from factory.

 

Yes, and, yes......