'74 widebody hot rod build

[rswannabe]

Mr Beau,

Yes, the motor has a vacuum manifold collecting signal from all six ports, combining them into one, and the manifold connecting to the MAP sensor in the Megasuirt ECU.

The scaling and smoothness of the VE table is still a work in progress. I'll be working to smooth the transition in those areas. It's hard to get to those cells solo on the street though :-). I'm hitting the dyno this coming week and should be able to sort those and other areas of the VE table safely.

TPS is throttle position sensor. It is reading correctly. The pull I posted the log for was not an all out full throttle run (stomp on the go pedal), but rather a roll into third gear on an onramp.

Yes, I just retimed the cams and they are absolutely balanced between the two banks. I saw the AFR difference before retiming the cams as well.

As i mentioned above, I am going to recalibrate the O2 sensors and swap them side to side to make sure it is not a sensor issue.

Ignition load uses the ITB load function which is a blend of MAP and TPS.

I'll take a look at that facebook group.

Thank you!

[rswannabe]

I spent about two hours on the dyno (Carburetor Connection in Totem Lake, WA) today with Chris Powell of Chris’s German Auto Service (Redmond, WA). Chris has many years of experience building and tuning hot rod 911’s and race cars. He’s more familiar with Motec and Haltec (he’s a dealer), but more importantly he knows stand-alone tuning of air cooled 911’s backwards and forwards.

I had not spent a lot of time tuning the full throttle portion of the tables and the dyno graph shows it. Here is a graph showing the before and after power curves.



Here is the final form.



There were a few hiccups along the way; such as realizing the head temp was bouncing around enough at the start of a pull to dip into warmup enrichment and briefly mess up the mixture. Once that was figured out, I dropped out the warm up and we finished dialing the fuel at WOT.

With fuel looking good, we started playing with the timing, but found there weren’t any gains to be had there over the ignition table I was already running.

Final numbers were 234 wheel HP and 230 wheel lb/ft. Corrected with 15% driveline loss that is 275 HP and 270 lb/ft at the crank. I’m fine with those numbers. The motor feels smooth and responsive and happy throughout the entire rev range.

[al lkosmal]

Looking good Brooke. I've been sending some of the local EFI/M'squirt to Carb Connection. They are good...and of course, Chris is the man.

regards,
al

PS: it is a bit tough to tune that top 10% on the road...remind me to tell you about getting stopped, by a State Trooper, for doing 110 on a tuning run on one of the frontage roads up North......... it's smart to save that for the dyno....

[rswannabe]

Al,

In regards to tuning on the street, I’m trying to not take any risks. Discretion is the better part of valor and all that…. Hence the dyno time.

Ticket for 110? Ouch!

Troy at CC was also very helpful and knowledgeable. He knew some of the ins and outs of MS and TS better than Chris or I.

[jpnovak]

Congrats on getting the EFI sorted. Nice smooth power delivery on those plots. Should be super fun to drive.

[rswannabe]

Originally Posted by jpnovak

Congrats on getting the EFI sorted. Nice smooth power delivery on those plots. Should be super fun to drive.

Thanks Jamie! Your help in getting to here is hugely appreciated. There will still be continued tinkering with the tune, but is in really good shape as it is.

Remaining refinements:

1. Dial out the few remaining pops on decel (or go full burble? - JK)

2. Sharpen the free rev throttle blips

3. Smooth some transitions in the VE map

4. Add intake air temp sensor for overall temp corrections

[Mr Beau]

Congrats! Did you get the bank-to-bank variation sorted?

[rswannabe]

Originally Posted by Mr Beau

Congrats! Did you get the bank-to-bank variation sorted?

Not yet. I did recalibrate the o2 sensors and swapped sides. They still showed cylinders 4-5-6 as about .5 point richer. I rebalance the itb’s, including up at 3,600 rpm (my airflow gauge was maxed out by the air volume at 4000 rpm). I checked torque on the intake and exhaust manifolds. All that and the discrepancy was still there.

Next up is to swap sides with the injectors to see if that is where the imbalance is.

[jpnovak]

Are the O2 sensors and controllers powered and grounded to the exact same spots? If not, minor changes in ground resistance can cause enough voltage shift to read differently on the sensor output.

[rswannabe]

Originally Posted by jpnovak

Are the O2 sensors and controllers powered and grounded to the exact same spots? If not, minor changes in ground resistance can cause enough voltage shift to read differently on the sensor output.

The two sensors are powered and grounded identically. I have a single switched power lead feeding both units (through separate fuses before the units) and the two grounds from the controllers combining to a single feed to the same ground point.

[jpnovak]

OK. Just wanted to make sure. That is often an overlooked, yet important detail.

[rswannabe]

Originally Posted by jpnovak

OK. Just wanted to make sure. That is often an overlooked, yet important detail.

Thanks! I appreciate the input on what to check.

At this point I’m thinking that maybe the injector that replaced my failed one (even though same make, model, size, color) might not be well matched. I’ll swap side of the injectors and see if the imbalance follows.

[rswannabe]

So I swapped the injectors to see if there was an imbalance in their flow rates. With the injectors that were in 1, 2, 3 moved to 4, 5, 6 and vice versa, I still had the same half point richer reading on the passenger side. So it’s not the injectors. I think I’ll swap the injector driver feeds next to see if they are somehow getting different signals.

In the meantime, in preparation for some upcoming suspension changes I measured my ride heights at all four corners and was surprised to see the car is about 3/8” higher on the passenger side. I did not expect that! So I picked up a set of corner scales and weighted the car. Here’s the result.



The weight of 2626 (full tank of gas) was right about where I expected the car to come in. Having more weight on the drivers side (without driver weight in the car) is not was I was expecting as it was supposed to have been corner weighted during the last alignment. I’m going to have a talk with them.

Here are the weights with me in the car.



So my plan is to pull the 22 and 28 torsion bars currently in the car and go to 19 and 27 to soften up the ride and promote turn in and rotation. The current ride and handling is acceptable, but I would like more compliance for our crappy streets. More to come soon.

[nospiners]

The details on this build have been of the charts .. Thank you for posting !!!!!!!!!

[chrisbalich]

It's such a PITA to get weight over that RF corner. It's got me planning to relocate my oil tank from RR to RF. That, or adding balast. My car is light enough that I can get away with adding 150lbs and still be lighter than most g-bodies.

[rswannabe]

I’m no expert on corner weights, and I’m not going to chase this now before swapping bars, but it looks like I could lower the RR to remove some of the cross jacking to the LF and that would simultaneously load up the RF and LR. It would also remove some of the higher ride height in the right side. I might be wrong in that though.

[rswannabe]

I swapped the new torsion bars in and rebalanced everything. I was able to get the cross weights dead on with me in the car with much closer front corner weights as well.



I’m happy with those weights, but I dropped the car lower than I wanted to while chasing the weights. I only really noticed after the fact, so I’ll be redoing the ride height and corner weights in the near future.

While I was in there I also swapped out the Rebel Racing RSR 25mm adjustable sway bars for a set of Tarett 25mm adjustable sway bars I picked up used. I did this because I want to use the more vintage looking RSR sways on my ‘69 911 and I was ok with the the look of the red Taretts on this car.

M

[Flojo]

edit: found info for brakes on page 1. thanks

[rswannabe]

Flo, the brakes are 993 calipers over 930 rotors and a manual 23mm master cylinder. The front rotors are the later fixed 930 rotors and not the earlier floating ones. The hubs are billet aftermarket, but are identical dimensions to stock hubs.

The full details and breakdown are on the first page of this thread.

[rswannabe]

I was able to reset my ride height and corner weights without reindexing the torsion bars; thank you Elephant adjustable spring plates! Here are the final weights with me in the car and out.