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Posted by: Racer Chris Sep 9 2003, 09:38 AM

I made four runs on the DynoJet at J & M Corvettes this morning after warming up the engine and made a few jetting adjustments.


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Posted by: Racer Chris Sep 9 2003, 09:41 AM

Here's a graph from the last run. The A/F ratio was about 12.7. On the previous run it made 2 more hp but was a tad lean at 13.7.


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Posted by: KenH Sep 9 2003, 09:45 AM

Looks good.

Now you know your shift points.

How about the specs for the motor.

Ken

Posted by: synthesisdv Sep 9 2003, 10:43 AM

Is this power to the wheels? Also, what is the engine displacement? 1.8?

thanks,
david

Posted by: Racer Chris Sep 9 2003, 11:08 AM

See this thread for lots of pictures of components and modifications. http://www.914world.com/bbs2/index.php?act=ST&f=2&t=4472

The bottom end has about 15 race hours on it already.
Stock 66mm crank; balanced; lightened flywheel; stock rods. Web 86a cam with Johnson lifters (purchased before problems started happening to other people); .435" lift, 290deg seat to seat duration.
New stuff includes 42 x 34 stainless valves; HD single springs; titanium retainers; new guides and seats; chrome-moly pushrods. Hand ported by me with no flow bench work; 38.5cc combustion chambers; 11.4:1 actual compression ratio. 94mm Nickies cylinders with custom JE pistons and ARP head studs.
110 Sunoco Standard fuel fed by Holley Red pump to 40IDF carbs; 36mm primary venturis and custom modifications with 2" v-stacks protected by custom screens & no filters. Exhaust is Tangerine Racing Improved Super Header with Phase 9 Silencer. Cooling system is flat (modified Corvair) fan under custom fiberglass shroud. No alternator. Front mounted oil cooler, 2 stage CB Perfomance oil pump - dry sump; Canton oil filter.
Instrumentation includes: 4 EGTs, 2 CHTs read by EI digital, scanning aircraft readout; oil pressure and temperature gauges; VDO 10K rpm tachometer; oil warning light; cooling fan warning light; volt gauge; mechanical fuel pressure gauge.

Posted by: Racer Chris Sep 9 2003, 11:09 AM

That's what a DynoJet measures.

Posted by: URY914 Sep 9 2003, 11:11 AM

Go get 'em.

Paul

Posted by: garyh Sep 9 2003, 11:55 AM

FWIW, A/F of 13.7 is more desireable then 12.7.

It's supposed to be range 13.2 - 14.7 (Max power to Min emissions)

At least according to the German/American/Japanese scientists and engineers that design gasoline powered engines.

Posted by: Brad Roberts Sep 9 2003, 11:59 AM

I like the curve but that is one hell of flat spot from 3600-4200RPM. I think your porting is a little too much for the "baby" camshaft. Whats cool is.. it looks like it will pull like a freight train from 4200 and up (which is what you want as long as the tranny is geared for it) Should be a blast. Mid-Ohio likes small sports cars with some torque.


B

Posted by: ChrisReale Sep 9 2003, 12:43 PM

I m looking forward to the run-offs asw ell, especially from a couch point of view!

Posted by: Bleyseng Sep 9 2003, 01:12 PM

Gary,
I think Chris wants to keep head and piston temps down using the rich mix to help cool them off. Even the factory Djet FI had the WOT mix set to 12.7 to 1. The water cooled guys live with the high a/f mixes.

On the turbo 2 mazda's we run the A/F at 11 to 1 for safety reasons. You can darn near watch the gas gauge fall but look out when you mash it.

Geoff

Posted by: Jake Raby Sep 9 2003, 04:06 PM

Looks great! looks like my pushrods worked out well for ya!

Posted by: Racer Chris Sep 9 2003, 04:46 PM

The run was actually started at 3500rpm when I mashed the throttle. The accelerator pump is a little too strong I think, which made it go way rich at first. Too bad the A/F curve wasn't printed out too.
I plan to keep it above 4400 as much as possible anyway. My gearing graph indicates that this will be no problem.

Gary, since I don't have EFI with O2 sensor feedback and/or anti knock sensing it's important to me to stay somewhat rich of max power. Much safer that way. And - what Geoff said.
Since one air correction jet size was enough to make a whole point of a/f difference I may ream an in between size to dial it in even closer. I rely on exhaust gas temps on track to make final adjustments.

Jake, yup. I used .080" shims under the rocker stands and still had to cut away a lot from the rockers for the swivel feet to clear.