Bf Mk2.5 Home Build - 309Rwkw On 15Psi

[JETURBO]

Good onya for getting it to the track mate

For a bit of ref on the 1/8th we have a customers ute that is a very keen 1/8th racer and his came up at 307rwkw

He does 7.3-7.4 repeatedly with 1.6 60's

He went 11.65@119mph on the 1/4 last sunday so u can see where u can head for on ~300rwkw

[IT15ON]

Confession time....

The tuning issues at the drags. There was a loss of power around 3/4 track. It was very sudden and pronounced, and we had been data logging for the runs (as advised ) because being bit closer to home the gear was available. After pulling a touch of timing and boost it still couldn't be explained.

Over lunch we considered what it could be. There was no reason that we could think of for this to be happening, as it doesn't happen on the street, or dyno. The one variable is slicks and heavy acceleration. The fuel guage was showing a touch under half (I had topped it up on way) which I thought was enough, but we thought maybe fuel was getting away from the cradle. Wanting to rule it out we decided a quick trip to the servo on the slicks would be worth trying. Ran it in to town and filled up, back to the track in time for eliminations. At the servo we were very surprised to see it take 41 litres to fill. The guage lies!!!

The first two elimination rounds I was running fast. There was no surge issue to be seen but I was running fast on my dial in, and the cars chasing me down were miles back. I smashed the brakes over the line in one run, for fear of breaking out. I believe this was a 8.49 on 8.05 dial, the torana just had wheelspin off the line. Next up was a Late model camira ute, and similar story, no surge issues for me but I was rolling over the line waiting for him to come closer - this run ended up being an 8.091 at 137kmh rolling over the line, on an 8.05 dial.

If I won the next race I'd be into the top two I believe, and the pressure was building. I was worried about breaking out so lowered the dial in to a 7.95, which may have been ambitious in hindsight, but I knew if I ran this quick I'd be happy win or loose. Surely enough, red light by .071. Leaving the line I saw the red and just went for gold, running the 8.057 at 146.84km/h/ This was a 2.012 60", so maybe a 7 sec pass if I got the launch right. There was no coughing or anything during this run, nice and clean.

Anyway the lesson learned was that my car likes a full tank of fuel for raceday. Pump is up to the job but not running a surge tank seems to create issues with fuel slopping around in the tank.

Edited 20/05/15 07:08 AM by IT15ON

[IT15ON]

Good onya for getting it to the track mate

For a bit of ref on the 1/8th we have a customers ute that is a very keen 1/8th racer and his came up at 307rwkw

He does 7.3-7.4 repeatedly with 1.6 60's

He went 11.65@119mph on the 1/4 last sunday so u can see where u can head for on ~300rwkw

Sounds like he is going pretty well, I'd be very happy with those times if I can get that out of mine.

There is clearly a lot of room for improvement in my 60" still. I think that's where a lot of the difference is. The best 60" I got for the day was 1.974. I am on ET Streets but we are looking to run lower pressures next time around. I was running 22psi. I think there's improvement to be made in the driver too though which will account for some of it. Does he run those times on a regional airstrip style track or a proper prepped drag strip? Is he on here anywhere with his story?

One other thing I am still not sure about is how big a burnout they like. A lot of guys my age smoke the hell out of them but I don't think that is helping at all. A bit of smoke to warm them up but still working out what is enough/what is too much.

All good fun, it's good to have a target to aim for time wise.

[JETURBO]

What your doing has been done HEAPS of times so ill help u out a bit

275ET's like around 18psi warm

Spin the tyres in the water box, as soon as u get 1/2 way through 1st short shift grab 2nd pin 2nd and as soon as u can grab 3rd and let off the brake and keep it spinning in 3rd as you roll out the water box , keep it going until 1/2 the distance between the water box and stage light

Shouldn't need to go past the stage light like so many plug holes like to do with their super loud but slow v8's

This will generate a bit of smoke but not to much ( enough to see in the wing mirrors but not enough to see in the rear vision if that makes sense ) ?

This method has proven me well to 1.7's and out ute customer to 1.53's

He goes to all types of 1/8ths so some air strip some semi prepped but he's a bracket racer and takes home the money 9 times out of 10 so its reliable

[IT15ON]

What your doing has been done HEAPS of times so ill help u out a bit

275ET's like around 18psi warm

Spin the tyres in the water box, as soon as u get 1/2 way through 1st short shift grab 2nd pin 2nd and as soon as u can grab 3rd and let off the brake and keep it spinning in 3rd as you roll out the water box , keep it going until 1/2 the distance between the water box and stage light

Shouldn't need to go past the stage light like so many plug holes like to do with their super loud but slow v8's

This will generate a bit of smoke but not to much ( enough to see in the wing mirrors but not enough to see in the rear vision if that makes sense ) ?

This method has proven me well to 1.7's and out ute customer to 1.53's

He goes to all types of 1/8ths so some air strip some semi prepped but he's a bracket racer and takes home the money 9 times out of 10 so its reliable

I'll give your technique a shot next time I head to Sydney. The setup at Gunnedah doesn't give enough space to run without crossing the beams but you get the idea.

I get the idea with the smoke, that's about what I was getting at Gunnedah on a couple of runs, repeat repeat repeat.

[IT15ON]

U

Good run last night at the drags

[k31th]

nice smoke and pretty decent result 118mph tells the story

[IT15ON]

nice smoke and pretty decent result 118mph tells the story

Very happy with the result - wanted to run an 11 and made it!

It was an interesting night, we had data logging gear and learned a lot. The car was reducing throttle input on the start line when stalling up so I was only leaving the line with around 34% throttle and not enough boost. This has since been resolved last night on the street so I am expecting to get the 60" down next time. Good smoke = good runs was the other main lesson, getting that bit of extra heat in the tyres made them hook up nicely.

The coolant temp was also quite high during the middle of the night, because it wasn't getting the airflow, just sitting in staging lanes heatsoaking before a run. First run of the night was a 12.0, then went to a 12.3 with heatsoak. It was pulling timing to reduce knock because of the heat during a slow run. This was quickly resolved by turning the fans on permanently and circulating coolant between runs, which got the temp down and allowed the 11 sec pass. Last night an 82 degree thermostat went in and fan settings were adjusted to suit.

Can't wait to get back out again and see how it goes, aiming to stall to about 6psi for launch (on 255 ET's) and see what that will achieve, along with cooler temps.

Edited 12/06/15 11:48 PM by IT15ON

[Robos F6]

Try pushing it all the way to the line with the bonnet up. Only start it when you have too

[IT15ON]

Try pushing it all the way to the line with the bonnet up. Only start it when you have too

We ended up running it for a while with bonnet up and both fans on to circulate coolant and cool. Made a good difference. Not that it was boiling or anything but enough to kill power. Now that the cooler thermostat is in that should help too, but definitely will keep bonnet up as you said. I'll keep an eye on temps and depending how happy it is might let it run or if I get serious I'll stop being lazy and push