SBC tunnel ram

[prairiehotrodder]

i have a AEM failsafe AFR gage that has data logging. It works really good. Last season i used it lots to tune my car at the track. Once i figured out what main jets my motor wanted (on my t-ram the carbs wanted to be a couple jets richer than the factory single carb jetting) i would check the data logging after each pass and note the shape of the fuel ratio curve. I then changed the HSAB to try and flatten the curve. My car kept going faster as i did that. I thin i ended up with a couple jet sizes richer on the main jets and couple sizes smaller on the HSAB from what the carbs came with out of the box intended for single carb applications. I'm no expert but this is my experience. DO NOT TRY AND WATCH A AFR GAGE WHILE YOU MAKE A PASS !!! I nearly hit the wall once at 135 mph. Thats when i got the gage with data logging.
Brian

[PRH]

Here’s an example of where the TR is doing what you’d like it to do:

540” BB Mopar, Indy -1 heads, 281-292-112 cam.

440-2 intake with 4150/4500 adapter, 1150 carb:
693tq @5300, 805hp @6800..... 794hp @7300
Bsfc @ peak - .48
@ 7300 - .49

Swap to Indy TR, two early non-HP 9375 carbs, stock jetting 92/92:
706tq @5600, 820hp @6600..... 806hp @7300
Bsfc @ peak - .49
@ 7300 - .54

Re-jet carbs to 85p/86s:
712tq @5700, 848hp @ 7300(new peak)
Bsfc @ peak(7300) - .45

[F-BIRD'88]

i have a AEM failsafe AFR gage that has data logging. It works really good. Last season i used it lots to tune my car at the track. Once i figured out what main jets my motor wanted (on my t-ram the carbs wanted to be a couple jets richer than the factory single carb jetting) i would check the data logging after each pass and note the shape of the fuel ratio curve. I then changed the HSAB to try and flatten the curve. My car kept going faster as i did that. I thin i ended up with a couple jet sizes richer on the main jets and couple sizes smaller on the HSAB from what the carbs came with out of the box intended for single carb applications. I'm no expert but this is my experience. DO NOT TRY AND WATCH A AFR GAGE WHILE YOU MAKE A PASS !!! I nearly hit the wall once at 135 mph. Thats when i got the gage with data logging.
Brian

Keep an eye on this guy. He has a good handle on all this IMHO

[555RAT]

DO NOT TRY AND WATCH A AFR GAGE WHILE YOU MAKE A PASS !!! I nearly hit the wall once at 135 mph. Thats when i got the gage with data logging.
Brian

Thanks Brian, good laugh on that one! Thanks for sharing your experience with this stuff. I can't hardly remember to watch the gauges on a pass so I was using my go pro, might have to change how I do that with the new rules on how to mount them. I do have an innovate MTX afr gauge I need to find a way to weld a bung on the collector somewhere.

[MadBill]

Is that via a data stream? I haven't tried it yet, but being somewhat tech-averse except by necessity, is it possible to video an AFR gauge?

[555RAT]

I use it for all the other gauges to replay a visual of what happened on the run. I haven't tried it with an afr gauge, it may not work very well. I have seen the same gauge on you tube though. I'll have to look and see if I can use the grid with that afr unit.

[555RAT]

Well, after a season of tuning and racing I have come to the conclusion that the tunnel ram is indeed more consistent AND faster, which was expected, than my single 4 setup. After trying different shift, launch, timing and jetting changes there are several things I noticed throughout the season which are the tunnel ram is more sensitive to changes and actually wants a bigger jet, which I think was said by someone earlier, and my fuel distribution is more consistent from cylinder to cylinder, hmm. More often than not I ran the same dial in from 1st round on just as one of my friends that runs methanol. It was a great season of testing and tuning and ending with a big win! It does take some time and effort but well worth it.
I just wanted to share my experiences with a tunnel ram in a race situation and thank you for the help and suggestions. I'm calling this season a success and had a lot of fun tuning this thing to my fastest ET and most consistent it's ever been!

[BobbyB]

Congratulations! Did you ever do any data logging as some suggested?

[555RAT]

I never got a chance to wire up the O2 sensor or measure to see if the wire will reach the gauge in the dash, may need the longer harness. I'm sure there is more gain in it by fine tuning with the o2 sensor though.

[555RAT]

Once i figured out what main jets my motor wanted (on my t-ram the carbs wanted to be a couple jets richer than the factory single carb jetting) i would check the data logging after each pass and note the shape of the fuel ratio curve. I then changed the HSAB to try and flatten the curve. My car kept going faster as i did that. I thin i ended up with a couple jet sizes richer on the main jets and couple sizes smaller on the HSAB from what the carbs came with out of the box intended for single carb applications. I'm no expert but this is my experience. .
Brian

Even without the AFR gauge I still ended up doing just this, a .028" hsb and 2 sizes larger on the jet than the single carb shows best on the time slip!

[prairiehotrodder]

I'm glad it worked out for you . I'm real happy with my tunnel ram. I ended up going another 2 sizes richer yet on the MJ and i went faster in the cool morning air but slowed down in the afternoon. I'll go back to just 2 sizes richer from the out of the box calibration.

How fast did you go ?

Brian

EDIT: i see you are running a pair of 950's ? Which carbs exactly are those ? I've been thinking of trying bigger carbs. Mine are the 750 track warriors on my 555 BBC.

[555RAT]

Thanks Brian, I ended up 8.004@163 dragging the brakes so not to brake out, 165 all out. Just missed a 7 second time slip. I could've gone up 2 jets and got it but didn't have the jets at the time and it ran that number repeatedly. In the 1/8 on the last weekend it ran a string of 5.03's at 135. These carbs are the 1.45" venturi quick fuel main bodies still shifting at 7500 simply because it's a bracket car and it repeats where it's at, might try 8k next season just to see if it picks up.