BUILD THREAD 86 GP 2+2~Blown 6.0

[64nailhead]

Are using the clutch or rowing?

Way to go on the 60’s - that’s damn impressive with a stick imo!!!

 

[81cutlass]

Throttle flat to the floor
Stab clutch
Shift
Let out of clutch

2 step turns on between shifts

 

[81cutlass]

Good news the car made it home fine! 900 miles and all that broke was a fuse (probably from when I pulled the trans 2 weeks ago and I never had flex content working for the last week and a half) I feel pretty successful that I broke the 'curse' of blown driveline parts.

The 53 ford tudor flathead got second in the bracket class, 18.69 dial in, ran a 18.691 and 18.690 in the 2 rounds! It broke out with a 18.46 the last pass to loose to the grey bracket race chevy pickup with a 10.44 dial in

The Z06 and ZL1 took 2nd and 1st in the factory street category, the ZL1 ran 9.80's and the z06 is a 10.04 car.

Malibu took 1st in 'outlaw' which is no limits, real low 8's average, it ran a 7.90 at 180 on day 2. Orange/black fox was in the 8.40's average

White fox took 1st in limited street with a 8.60 ish and the black fox took 2nd with a 8.70ish something.

A flathead, SBC, 2 LT's 1 LS, 1 SBF, and 1 coyote, and one BBC powered the top cars.

So a few interesting points once I look at the data.

1. I don't think my syncros are out, I think something is screwy with my hydro TOB. I max my clutch line pressure sensor out (1000psi) on shifts. In neutral with the engine on or off it only takes 600psi of pressure max at the clutch but it spikes at shifts. Maybe the clutch isn't releasing all the way? The feel of the clutch did change through the weekend and it feels like the throw of the pedal has been reduced and it hits a 'wall' at the bottom instead of it being a little squishy. I didn't look at the logs closely enough at the races to see that pressure spike. That didn't occur with the old clutch. Needs investigation

2. The launch is consistent but I think there is more refinement from about 40ft on. The first 40ft is good and is getting me an acceptable 60ft time but it's setting me up for a poor 330ft time.

I was looking at a few other time slips of similar cars on drag weekend, one is an NA 6.0 2650lb t400 fox, and the other is a ~3200lb mildly rowdy 408 LS 4l80e Regal with an intake and some head work. The fox runs 10.80's at 125, the regal runs 11.10's at 122. I ran a 11.60 at 122. I would say my car for sure weighs the most. I did run a 1.62 60ft after this 11.60, 1.69 60ft pass but with the missed 2nd gear shift. What's off is my 1/8th mile. The fox and regal both put on 25mph on the second half where I put on 27mph. I am for sure making more power than both of those setups especially for me weight and although my 60ft looks good my 330 and 1/8th time are soft.

This is my 11.60, 1.69 60ft pass at 122mph. 2 step at 4600. The slipper is working but it does start to drag the RPM down starting about 0.8s into the run. It fully couples and 'bogs' at 1.42s into the run. From there on out it needs to 'lug' from it's poor power band of 2800 to maybe 4000. I really need to tune this out.

The 1.62 60ft had 4700rpm on the 2 step and 'bogged' to 2975.

I either need to allow the clutch to slip longer so it's not bogging the engine down as hard, or bump the initial launch RPM higher. What is saving me here is that the car is already moving 24mph by the time the clutch couples fully so it doesn't feel as boggy as when it happened at 8mph without the valve. I have effectively moved the coupling point deep enough past the 60ft that it looks good on the 60 but isn't generating the results at the 330.


As far as IAT's
11.5 PSI, 6200 shift, 113 start 154 end (1st pass, 62F ambient, plenty of time to cool blower off)
11.5 PSI, 6200 shift, 125 start 160 end
10 PSI, 6200 shift, 125 start 157 end
10 PSI, 6750 shift, 125 start 158 end

Adding boost and shift RPM made like zero additional IAT rise at the top. If it's 60-70 degrees outside the IAT's are going to hover about 155-160 at the top of the pass providing I give it some time to cool off (check over the tune, tire pressure, watch a pass or two, ect). The IAT's got to 165 last month during my testing when the ambient temp was 10 degrees higher and I hot lapped the car a bit more aggressively.



And to be fair on the 6750 RPM shift stuff, the tune was in complete disarray past 6250 since I have never ran there. It dropped under 11.0 at 6200 and hovered between 10.3 and 10.6 from 6250 to 6750. I said RPM=bad and didn't try it again. I only had 3 clean passes after this one, and 3 of them were boogered 2nd gear shifts.

So as things go, I got 75% of what I wanted done this weekend and discovered a bunch more things I want to refine and try again.

 

[Turbo Zach]

Very interesting all the systems you have engineered and data you have collected and shared. A lot of it is over my head, but interesting. What I do know is you have a fast car that you built that is different. Keep up the good work.

 

[64nailhead]

I'd let the clutch grab and pull timing. I wish I could tell you how to do it in HP Tuners, but ...I can't. Only reason for recommending that is you're going to turn into a clutch swapping expert.

 

[81cutlass]

Maybe I don't understand what your thinking.

I am not power excess to the point where I'm concerned about spinning, I'm power limited. I can't/don't want to fully couple the engine to the trans until the trans input shaft speed reaches ~3500 rpm. If it does couple below that point power is so limited it has to lug out of the range where it makes it really slow.

I am concerned about the heat for sure. It's a ceramic clutch and a few people (local expert included) that these ceramic clutches take heat well and you can slip them.

I want to try 3500rpm launch rpm and slow the clutch even more to see if that slows the 60ft down. Basically if 4500 or 3500rpm engine speed makes any difference on the power applied to the tire when the clutch is slipping.

 

[motorheadmike]

And to be fair on the 6750 RPM shift stuff, the tune was in complete disarray past 6250 since I have never ran there. It dropped under 11.0 at 6200 and hovered between 10.3 and 10.6 from 6250 to 6750. I said RPM=bad and didn't try it again. I only had 3 clean passes after this one, and 3 of them were boogered 2nd gear shifts.

Called it. Tune was jacked.

The difference between the Commanded and measured EQ ratio is substantial. Also look at your Cylinder (g) as that is the calculated air mass and correlates to your VE. The problem with your snap shots is the 6700+ is happening a lower speed/load and the 6400+ is at a higher set. The IATs are vastly different as a result. This isn't apples to apples. My guess is your Cylinder (g) drops to a similar point. Meaning there is an efficiency problem in either the tune or the supercharger.

In my humble opinion.

 

[64nailhead]

What Mike said (I think hehe). I'm not clear at all about what he's referencing in your log snapshots. But I believe there is something askew somewhere. You mentioned that there is bog or lull or something when the clutch fully couples. I just can't imagine that there is one with supercharger/blower setup. The HP curve should be extremely linear and on a steady uphill climb until you run out of blower. I do understand that there is a point where you make max boost, but that would seem that it should be well below 4000 rpms.

It appears that you're at 10psi at 3000 - my god that 6.0 should be hitting like a freight train at 10psi at 3000. The last thing that should be occurring is a bog imho.


EDIT : I might be wrong on this, but golly, I don't think so. Please don't take my word as gospel. I'd really love to see some dyno tuning with this.

 

[81cutlass]

Called it. Tune was jacked.

The difference between the Commanded and measured EQ ratio is substantial. Also look at your Cylinder (g) as that is the calculated air mass and correlates to your VE. The problem with your snap shots is the 6700+ is happening a lower speed/load and the 6400+ is at a higher set. The IATs are vastly different as a result. This isn't apples to apples. My guess is your Cylinder (g) drops to a similar point. Meaning there is an efficiency problem in either the tune or the supercharger.

In my humble opinion.

Good idea starters.

The more I look, the worse the tune is, lol. Hindsight is 20/20. I really went into last weekend with a crap fuel tune. Now that you made me look, it's been crap ever since I put the twin pumps in and never realized it. The old tune (single pump) was pretty much dead on fueling and I luckily balanced low fuel pressure with almost maxed out injectors. Now that the fuel is there the VE is wack, and it has taken a lot of changes to get it in spec. I honestly wouldn't be surprised if the engine was running at below 10:1 AFR but the wideband was out of range so I just kept taking fuel out little by little for the past few months.

-My injector duty cycle is 80% at 6200 rpm and is 105% at 6500. It's just dumping in unnecessary fuel. 1.53g at 6200 and 1.8g at 6500. I see to remember I semi tuned it to look 'pretty' when I had a single fuel pump so the VE continues past the normal RPM range. Not knowing I didn't have enough fuel flow just added VE to add injector duty to get the fueling in spec. Now that I do have the pressure stable in boost it's over-fueling those areas that I haven't fixed.

After about 10 passes and 5% VE adjustments on almost every pass, I am happy with the AFR in the 4600-6200 range, bouncing from 11.3 to 11.7, I command 11.5 in boost. Good enough. I started in the 10.5 to 11.1 range Saturday AM.

The VE is about 100-106 in that 4600-6200 range where it is fixed and holds around 11.5. The un-tuned region at 6400+ is 120 VE so it dumps another 20% fuel in there and yeah, I can see why it is choking. It doesn't fully explain why


My list of to-do's was long enough to get the car to launch that I never looked at the power band and where I should be shifting. I think I am there now. Another thing to add to the list.

What Mike said (I think hehe). I'm not clear at all about what he's referencing in your log snapshots. But I believe there is something askew somewhere. You mentioned that there is bog or lull or something when the clutch fully couples. I just can't imagine that there is one with supercharger/blower setup. The HP curve should be extremely linear and on a steady uphill climb until you run out of blower. I do understand that there is a point where you make max boost, but that would seem that it should be well below 4000 rpms.

It appears that you're at 10psi at 3000 - my god that 6.0 should be hitting like a freight train at 10psi at 3000. The last thing that should be occurring is a bog imho.


EDIT : I might be wrong on this, but golly, I don't think so. Please don't take my word as gospel. I'd really love to see some dyno tuning with this.

The bog/lull isn't something I can feel honestly. Maybe I am focusing on it too much. I probably should stop saying bog. The better word is probably power band. I want the engine to be out of that sub 3000 rpm range and more in the power band. It's just easy to see on the logs that the engine sits in 1st gear for a long time and although 10PSI is awesome, the engine just doesn't make the power at sub 3000 rpm that it does at say 4000. It makes 9 PSI at 2300 RPM WOT. I'd really rather NOT put 9 psi on the pistons at 2300 rpm. If I run into traction issues I'll pull timing, but I really don't want to have the engine under that much boost at low RPM if I can help it.

I do agree that the engine must be making a ton of power down low. It ran 1.67 60ft on this pass. I had the 2 step set to 4000 RPM and after 0.95 seconds it pulled the engine down to 2340. It ran a 1.67 60 ft and the engine never exceeded 4000 RPM. 0.58 seconds of the 1.67 60 ft time were spent under 3000 RPM.

So I am entertaining the fact that you are right, or at least taking it as a suggestion. Maybe it's not an RPM issue. It's still a bit rich in the 2250-3500 range so maybe thats why it's slow past the 60ft?

What Mike is referencing is the rise in gram/cyl because my volumetric efficiency table (VE) is total trash. It is tuned where I run the car often (4000-6000 rpm) but past 6200 I have never really run the car and it's hot garbage. The blue box on the left is what the g/c should look like, flat, maybe a slight rise, but what I get is a MOUNTAIN of additional g/c in the blue circle to the right of the white line at 6179 RPM.

I need to fix my fueling before I make any more rash decisions.

 

[81cutlass]

Very interesting all the systems you have engineered and data you have collected and shared. A lot of it is over my head, but interesting. What I do know is you have a fast car that you built that is different. Keep up the good work.

Thanks! Yeah I will keep at it. I told myself I won't paint the car until it runs 10's. It needs paint. So it better run 10's haha!

I had one guy call the car a 'museum piece' at the track Sunday so there's that 😉