Got some data from racepak this weekend. Looking thru data, i see the carb pressure is fluctuating from 9.3 to 10.7 and back down. Is this normal to see from those used to looking at racepak? It's consistently doing it. My 60ft times where all very consistent... had to abort a few runs due to down track traction. No prep, and 30 degree air temp

Main question is the fuel pressure...

Is it from wheel stand bouncing floats?



Thanks

This message has been edited. Last edited by: ski_dwn_it,

there is a lot of stuff on that chart but does the fuel pressure fluctuation loosely follow your G meter?


Joe

Gday,
What sort of pump, what regulator, deadhead or bypass?
Cheers
Paul

quote:

Originally posted by ski_dwn_it:
i see the carb pressure is fluctuating from 9.3 to 10.7 and back down. Is this normal to see from those used to looking at racepak?
Is it from wheel stand bouncing floats?

NO and NO

That said...

1. why would you put your car in the beams on a track that wasn't prepped and in 30 degrees?

2. why are you running fuel pressure over 9 psi?

3. why would you post that mess of a graph?

quote:

Originally posted by Paul Dilley:
Gday,
What sort of pump, what regulator, deadhead or bypass?
Cheers
Paul

Magnafuel pro star 500, new filter. Dead headed regulator (setup patrick at prosystems provided when i tried his carb, and APD confirmed was fine for their carb then replacing the pro system SV1. Both Alcohol. -12 to pump, -10 everywhere else.

Yes the fluctuation follows the gmeter.. that is why i graphed it as well. Legend above shows the key.

Pressure was originally set with autometer guage at 9psi, the racepak sensor reads slightly higher. Ran it exactly where it was set on these runs for 2years. Car only varies a few thou on back to back runs... especially the 60ft where its fluctuating the most.

Your fuel pressure is too high and I’ve watched your car launch in route to a first round loss. It don’t work well and is not consistent.

I would agree that's a lot of carb pressure. You've got a problem somewhere in the tank/pickup/pump area ...... carb pressure should never vary that much with G meter. It will follow varying pump pressures though.



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This message has been edited. Last edited by: XPS fan,

Here are the slips. Again 30degree, no prep, breaking the beams with rear wheels every pass.

The 9psi was recommended by pro system and apd both.

not bad for a car launches like violently and run on an ice rink it has no business being on.

That said, I don't care who said to run the pressure that high, it's too high.

Oh and when I set up to break the beams with the slicks, I run 1.30-1.31 60 foots.

next question, what direction is the sensor facing? it should be straight up or to the side never front to rear.


Joe

quote:

Originally posted by sr4440:
next question, what direction is the sensor facing? it should be straight up or to the side never front to rear.


Joe

Joe,
The sensor is rubber mounted to reduce vibration vertically on the firewall, both the oil pressure and carb pressure are tilted slightly on a 45-60* angle side to side so I can get at the plugs. But front to back they are vertically up the firewall. No front to back tilt.

One thing I am always picky about (and not sure it matters or not) but getting all the air out of lines that feed sensors. And in this matter because I was alone on the install I did not "bleed" the air out. Could it be trapped air compressing?

What pressure are the rest of you guys running with Alcohol? The 9.3 is higher by .3 than the autometer guage and I knew that going out, but didnt want to change anything else; being I just rebuild the motor and wanted to keep as many things the same.

Ed I am killing a ton of timing with the grid - if I turn it up the car STILL dead hooks but rides a wheelie way too far out for my liking - over 150ft arrow straight. I added back 2* of the many I was pulling Sunday and it did just that...and it went 1.32 I believe I can get the slip if you like. And big fat tired cars couldnt get off the line - and mine worked fine.

Many of the runs I only ran it to the 330ft to get some passes on the motor before this weekend.

Two runs I ran it the whole way once the sun broke through - arrow straight and weather system said 9.13 & 9.15 and it went 9.13 & 9.16 with a very strong headwind. 9.16 pass I pulled 4* on 1-2 shift, as the racepak showed a blip on the shift, likely why it varied or the wind.

When I lose its 99%, not the car. It's me and I can accept that.

Ed post some of your graphs for comparison of pressure through a run since the cars are similar and behave the same off the line. I know yours is better but still similar.

Jesse, I am breaking your balls but I'm trying to help you as I always have.

That said, your car does need suspension work at the hit.

As to my racepak files, I can post and/or send you graphs next week or you can come to Numidia next week for opening weekend of the Summit ET Series and view them in my trailer.

As to loses, most bracket racers lose more than they win except the internet forum heroes that post here.

This message has been edited. Last edited by: 1320racer,

Probably not up to Ed's standards but not a bad running car with carbs (.980 60'). In my experience the carb pressure is more effected by pump pressure changes than a direct relationship from the g forces themselves ...... and of course the g's have an effect on the pump/pick up.







.

quote:

Originally posted by 1320racer:
Jesse, I am breaking your balls but I'm trying to help you as I always have.

That said, your car does suspension work at the hit.

As to my racepak files, I can post and/or send you graphs next week or you can come to Numidia next week for opening weekend of the Summit ET Series and view them in my trailer.

As to loses, most bracket racers lose more than they win except the internet forum heroes that post here.

Thanks- yes send them. I am already booked for next weekend...and your track doesnt allow transbrakes in no-box which I need to use for grid trigger. Stupid - hence the reason I ran box (without a box) the day you saw me running last year. Wont see me there because of that reason - otherwise like Numidia and I used to go there all the time as you will recall - back when you were afraid to leave the mineshaft air with your chevelle to race me.

quote:

Originally posted by XPS fan:
Probably not up to Ed's standards but not a bad running car with carbs (.980 60'). In my experience the carb pressure is more effected by pump pressure changes than a direct relationship from the g forces themselves ...... and of course the g's have an effect on the pump/pick up.







.

Thanks. Do you guys run foam in your cells. The before mentioned carb folks told me to make sure I remove it - which I did.

I suspect that what I am seeing is a pickup issue - but the only thing with that is why the rise in pressure - the regulator should keep it to a max...

quote:

Originally posted by ski_dwn_it:
Got some data from racepak this weekend. Looking thru data, i see the carb pressure is fluctuating from 9.3 to 10.7 and back down. Is this normal to see from those used to looking at racepak? It's consistently doing it. My 60ft times where all very consistent... had to abort a few runs due to down track traction. No prep, and 30 degree air temp

Main question is the fuel pressure...

Is it from wheel stand bouncing floats?

I'd like to see a one run not the 6 overlaid. I'd like to see RPM, DS, AF, Fuel press and G.

Generally speaking electric pumps usually show very little chop. Belt drive tunnel ram - another world.

Regarding the wheelie IMO, just take out a lot more timing and longer duration - it will stay down.

This message has been edited. Last edited by: Greg Kelley,

FWIW I have NEVER seen pressure fluctuation on a racepack like you posted, they generally look more like the one XPS posted. Even downtrack where the G's would have zero affect it is wavering a ton. I would look over the system from front to back again. Cant imagine it being a G force thing as it goes UP at the hit and you say its carrying the front end then? Is the cell up front or at the rear?

I don't use foam and never have.

Yes, foam in my cell.

Numidia, NHRA Division 1 does NOT have a no box class. Pro ET is a Footbrake class.

quote:

Originally posted by ski_dwn_it:
Thanks. Do you guys run foam in your cells. The before mentioned carb folks told me to make sure I remove it - which I did.

No foam in any of the heads up stuff I work on/build ...... and a lot of the tanks are fabbed to fit in an available space. They do make foam that is compatible with alky if you wanted to try some.



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