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 Post subject: The MGB is now a 9 second car. So what to do next ??
PostPosted: Wed Jul 17, 2013 8:31 pm 
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Joined: Thu Apr 19, 2007 7:45 pm
Posts: 3963
Location: Bucks
Stick with me folks!!
I'm throwing thoughts and ideas out now ;)

On the last outings the MGB has run:
9.96 + 9.96 + 9.95 + 9.90 + 9.81... So I'm now happy that the first 9 was not a fluke. All of these runs were with 13psi of boost + 150 shot. I just adjusted the FRED settings to improve things. I only get 13psi at 5800-6000 rpm. While the engine revs rise the boost runs from 6psi at launch up the the 13psi by the time I shift gear at 6000rpm.

As Trev has already mentioned, the launches are quite lazy. And I'm sure that I can get the high 1.5's and low 1.6 60 foot times back down the the 1.4's I used to run on nitrous only by adding more gas a bit quicker.

But I dont really want to go back to 4 pulsoids, so maybe its time to keep the clutter out of the engine bay and buy some bigger pulsoids to run 4 crossfires in the plate. I assume I can just fit my Y connectors to the bigger pulsoids to run 4 crossfires? I know that the 4mm lines to 4 crossfires will flow 240-250hp no problem.

I'm happy that FRED will do what I want as I do full throttle shifting with the auto box. So all I need is a start power setting + a ramp time setting.

The engine is now bored and stroked out to 4889cc and the CR is now 7.5:1 with Omega forged pistons. I've just been messing around with engine fuel settings. With the boost + nitrous I'm keeping AFR steady at mid 10 to low 11's so its safely rich. The low comp engine ran all the 9's above with only 3 degree's of timing taken out. I havent had it on the dyno yet because I just havent had the time. Plug readings have shown a nice sooty thread ring with a slightly sooty insulator which is dark grey at the top. Earth strap shows black at the bottom and clean to the bend where it then gets lighter in colour to the tip. No signs of speckles anywhere on the plugs. No signs of deformation of the end of the earth strap. So I guess I'm in the right ball park.

I wont put it on the dyno until I find some road tyres or drag radials for the rear. The slicks dont like the dyno. I melted a set last year with only 400hp and 500 ft/lbs on 7psi of boost as they slip too much under load. I wrecked another pair before that as well on nitrous only when she was making 380hp at 600 ft/lbs with a 300 shot. That was on the old engine which was 9.3:1 CR.

So I now have a Rover V8 which should be able to top 600hp (maybe it allready has, I wont know until i get it on the rollers) which is pulling strong. With my 9.81 PB I ran 138mph. Last weekend with a bit more power on the launch I had wheelspin in 1st and only ran a 10.00, but at 139.62mph. So a lower ET but more mph ??

I'm thinking that there is a lot more to come from this engine now. I know the old 9.3:1 CR engine with stock rods took 12psi of boost with a 250 shot fixed hit straight off the line for about 300 feet before I bent a stock Rover rod. This was with 12 degree's of retard.
The Chevy Rods I have fitted now are good for 700hp apparently. So a lot stronger than the old stock rods. The new low compression engine seems happy with less retard. I'm not taking any timing out for the boost. And I'm only taking 1 degree out per 50 shot of gas. I did try 2 degree's more retard and she ran 10.1 @ 134mph.

Sorry if it sounds like I'm rambling now, but I'm just thinking out loud if that makes sense :)

Given the results on track for the last few weeks I'm thinking I should be looking at a 200 shot with a 40% start and a 1.8 second build time to start with.

Now my thoughts turn to ign timing. As the engine rpm increases do I need to stick with a fixed ign timing setting? I launch with the ign retard fixed. Should I add timing back in at high rpm?

Over the winter I will be adding some lightness to the car which should save me 60lbs in weight. I'll be fitting a new exhaust system which should give me another 25hp and save even more weight.

I may even add 2" to the rear wheels to go up from 8" slicks to 10" !!


These are my ramblings folks. Please feel free to chip in with your own thoughts and idea's. As Trev has said. I dont see why a 9.5 could not be possible with a hard launch. I'm now looking at the bigger picture for next year with more nitrous and a longer build time to see if a 9.00 is possible with weight loss mods ? :)

Perry

_________________
1975 MGB Rover V8 aka Slim Rabbit 9.62 @ 137.37 mph with 175 shot.
9.59 here I come !!!!


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 Post subject: Re: The MGB is now a 9 second car. So what to do next ??
PostPosted: Wed Jul 17, 2013 9:39 pm 
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Learner

Joined: Fri Sep 02, 2011 7:21 pm
Posts: 151
Congratulations!, you've worked hard for it and well deserved!.


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 Post subject: Re: The MGB is now a 9 second car. So what to do next ??
PostPosted: Sun Jul 28, 2013 12:09 am 
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Joined: Mon Jul 08, 2013 10:46 am
Posts: 6
What to do next? Simple...whatever it takes for 8 seconds :D Awesome times by the way!


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 Post subject: Re: The MGB is now a 9 second car. So what to do next ??
PostPosted: Sun Jul 28, 2013 8:45 pm 
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Wizard

Joined: Thu Apr 19, 2007 7:45 pm
Posts: 3963
Location: Bucks
1sloZ wrote:
What to do next? Simple...whatever it takes for 8 seconds :D Awesome times by the way!


Ha Ha!!
Could be as simple as new pulsoids and a new controller + mods to the ign system, or Mega expensive mods to chassis and rear end + transmission. I'm halfway there with the tranny as I have another th350 gearbox with transbrake kit fitted and ready to use. But the transbrake could wreck the rear axle?

I'm very very pleased with this years testing on the new build since we rolled it out early in june. Its more than made up for a year off track with a blown engine. I'm almost sure that I can find the 0.22 of a second to break into the 9.5's before the year is out if everything holds together.

But trying to find another half a second on top of that is going to take some doing on a cheap budget I think :omgrofl:

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1975 MGB Rover V8 aka Slim Rabbit 9.62 @ 137.37 mph with 175 shot.
9.59 here I come !!!!


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