5.73@122.1 DRW/Buick new best.

[Underboost]

Originally Posted by DonWG

I use a stock heat range plug. It still ends up fouling on the gas if I play with the car too long on gasoline. The long cam causes that. I use the same plug on the alcohol. After one run, the plugs are nice and clean again. I run the nitrous such a short time and the alcohol mixture so rich, that I don't need a cold plug.

I use NGK Iridium. They seem to last the longest before fouling when on the gasoline.
Part no. BKR9EIX, I think.

That makes sense.
I once bought a set of Denso Iridium plugs after I read the article Duttweiler wrote $75 I never did get to run them they where for the Irons. Maybe I'll get some for these M&A heads.

[DonWG]

I just wanted to note one of the many virtues of burning pure methanol for racing, compared to gasoline.

You can run your a/f mixture as rich as you want and NEVER worry about fouling a spark plug.

[TurboTR]

I found that the back pressure varies with rpm. It's been > 10 years ago now since I was running a 76 q trim (w/ both .68 and .84 a/r hsgs for it), but I measured the back pressure at about 40-50+ psig at only 25 psi boost. Dunno why yours would be any different. Seems like even just a GTQ76 would probably be a very nice upgrade for your app. A GTS76 even better for your race only app. The GT series exh side just works alot better than the q trim in both spool up and in power. Its a different approach where the turbine blades are a lot wider, and there's one less blade to make room for expelling the exh.

TurboTR

[norbs]

Since he is using nitrous the gts trim would work nicely. The wheel is actually a gt42 wheel clipped down to fit the pte housing slightly.

[TurboTR]

BTW Don, you probably have discussed this in another post already, but what did you do for a camshaft? And what push rods are you using?

TurboTR

[V6QUICK]

Don keep up the good work. Everytime I log on I see progress and lower ET's the car keeps going faster and faster. It's nice to see someone working outside the box. Gotta love that spool up!!!!!!!!!

[DonWG]

Originally Posted by DonWG

I use a stock heat range plug. It still ends up fouling on the gas if I play with the car too long on gasoline. The long cam causes that. I use the same plug on the alcohol. After one run, the plugs are nice and clean again. I run the nitrous such a short time and the alcohol mixture so rich, that I don't need a cold plug.

I use NGK Iridium. They seem to last the longest before fouling when on the gasoline.
Part no. BKR9EIX, I think.

I had been using NGK BKR4EIX. It is a resistor Iridium plug. I had been using a 4 heat range in the past for warm up and racing. It was convenient because I didn't have to worry about fouling on the gas and I didn't have to change plugs at the track. To be safe though, I've decided to switch exclusively to the 9 heat range. The 9 is the coldest and safest. I may also be switching over to the NGK V power gap style. It is a non-resistor plug, which is the only thing I don't like about it. The thing about the V power is that I can more easily cut back the ground electrode for nitrous use. The ground electrode on the iridium plug is harder to work with because of the fragile iridium electrode, and if left alone, gets a little too hot with the use of the nitrous.

Combustion heat signs on the 9 NGK plug show the plating burned away to the first thread. Heat discoloration on the ground electrode about 3/4 the way back. This is with the iridium. I like ground electrode heat signs about halfway back.

[DonWG]

Originally Posted by TurboTR

BTW Don, you probably have discussed this in another post already, but what did you do for a camshaft? And what push rods are you using?

TurboTR

The camshaft is:
Crower mechanical roller. Specs for grind supplied to them by me.
242@.050 int.
248@.050 exh.
110 lobe separation
Installed 4 degrees advanced.
Crower mechanical roller lifters with oversized rollers, needles and .903" body.

Pushrods are single taper Mantons. 3/8 to 7/16 with 5/16 ball ends.

[DonWG]

Originally Posted by V6QUICK

Don keep up the good work. Everytime I log on I see progress and lower ET's the car keeps going faster and faster. It's nice to see someone working outside the box. Gotta love that spool up!!!!!!!!!

Thanks for the encouragement.

[DonWG]

OK. Finished digesting the latest datalogs from the 22nd.

By the last run, max boost for the weekend was 30 psi. As usual dropping to exactly 280 kPa at max rpm. A 280 kPa reading with my setup is just under 28 psi. The change to the .96 a/r turbine housing doesn't seem to have hurt anything except for a little more lag to spool to max boost after the nitrous shuts down at 16 psi. The thing I noticed is that when the turbo does get around to boosting, it seems to be coming on more violently, making traction a problem.
Best time was 9.29@145 on the third and last run.
There's still 2 or more psi to throw at it. Even though the boost level always seems to be limited to 280 kPa at max rpm, the boost controller can still control the boost level at the lesser rpms, like after a shift.
Using a shift point of 7,200 rpm, the drop in rpm between shifts is about 950 rpm. Shweet.

[DonWG]

If anyone is wondering what happened on that first run, I must have set the clearance of the crank sensor to the timing wheel too close or the sensor loosened and it contacted the timing wheel. The sensor was kicked back a good 1/2 inch. I was pretty lucky that it restarted at the line and I was able to get it back to the pits. After refueling, it wouldn't start and that's when I found the crank sensor problem. Simple readjust with more clearance and tightened down real good.

One area of the fuel map that needs work is the area where the auxiliary fuel rail turns on at 8 psi boost. Much of the area a little before and a lot after that event, up to 5500rpm/260kPa is grossly rich. Over 35 percent. You can see it in the latest videos. The car is lazy on the launch, even with the nitrous and then engine rpm comes up very quickly after that rich section has passed. That is probably the main thing that is causing the turbo to hit so hard at about the 50 foot mark, making traction an issue. The mixture is just coming around at that point. The next bit of testing will deal with leaning that area a little at a time to smooth out the launch. That will be done without nitrous, so I get clean readings. This last outing was all with nitrous (couldn't resist ), so I don't have that spool up time off the nitrous yet for you Norbs.

Also, I didn't get that exhaust back pressure. Even with the gauge staring me in the face the whole run. I was watching the tach too much. I'll keep it hooked up and try to get it next time out.

[norbs]

Funny as i was reading your post, i was looking for your results of the spool time, but mostly the BP reading, you could even test it on the transbrake quickly.

[DonWG]

Originally Posted by norbs

Funny as i was reading your post, i was looking for your results of the spool time, but mostly the BP reading, you could even test it on the transbrake quickly.

I tried that at the shop and got no, nada, zip, zilch back pressure reading.

I only stayed on the brake long enough to get about 2 psi boost pressure.

Should I be seeing back pressure building up right away? Or will I need to get to a higher boost level before I start seeing something? What have been the experiences of others?

[lazaris]

Don,

Your really not going to see any BP with 2psi. I sent you an email with an update.

[norbs]

Your should be at 15 psi within 3-4 seconds on the transbrake max! from idle.

[DonWG]

Originally Posted by norbs

Your should be at 15 psi within 3-4 seconds on the transbrake max! from idle.

The torque converter I'm using is very tight. 2400 @ 0 boost. For me to sit on the transbrake without nitrous assist, and wait for 15 psi is longer than I want to do. The last time I tried that was back when I was playing around with the 200C and I twisted the stator support shaft like a poppin' fresh roll of biscuits. I'll wait for the next pass to get the info.

Update on spark plugs. I was playing around with the gas program and came to the realization of why I went to iridiums in the first place for a warmup and gasoline plug. The racing plugs foul way too quick on the gasoline program. It's back to a hot set of iridiums for warmup plugs.

I got the engine running up on the gasoline nice and smooth now. You should see what the fuel map looks like. It's an unbelievable roller coaster ride. Pressure pulse waves in action. Unplugging the exhaust on that left bank made a big difference in fueling at low to midrange rpm. Didn't change midrange and upper rpm needs a whole bunch. Not what I expected at all.