z-ya

Yes, that is fine. As long is it is not below 0.5V or so.

I found out more information about the carbs. They are flat slide POSA carbs. This engine was used in a formula Vee racer for hill climbs and autocross. It has an adapter plate to bolt to the VW transaxle. The stub on the valve cover probably helped tie the engine to the chassis. Hear is some cool literature on the POSA carburetor: http://www.slickschoppers.com/TechArticles/Posa1 Learn some thing new each day!

Found this interesting L16 for sale. Never seen carbs like this.

Firefox rules

Actually, it won't. I = V*V/R The higher the resistance, the lower the current, the less power. My point is that the damage may have been done to the coil by the VB921 before the VB921 blew. Disconnect pin 36 from the coil when you first power up the MS with the new VB921. Measure the voltage on pin 36, it should show a positive voltage. If it is very close to zero volts, you have a problem, and you will most likely burn out another coil and VB921.

A higher resistance coil will draw less current and there fore is less likely to damage the VB921. Unless you damaged the coil when blowing the VB921. Double check your coil wiring before you put anew coil and VB921 in there.

Haven't firgured that out yet. I could run some clamp on K&N filters with some sort of velocity stack inside, or I might retrofit a stock 240Z air cleaner.

Take the IAC stepper motor off, and just adjust the idle screw so that the engine gets enough air to idle. After you get all the bugs worked out, you can revisit the IAC control. Too many variables in an equation makes it very difficult to solve. Hear is what I would do: - Make sure ignition coil is wired correctly to VB921 - Get a stable and reliable spark - Verify crank timing with timing light - Start engine. - Adjust idle screw on TB so that it idles - Adjust required fuel to get smooth idle - Verify that timing in the timing map matches the actual timing (with timing light). Change trim angle in spark settings so that actual timing matches the timing in the timing map - Put the IAC back on and debug that.

I built an 8.7:1 L28 for my Wife's 280Z. It is an all stock P79 motor (flat top pistons, P79 head) except for +1mm overbore. It makes excellent midrange torque, and is really fun to drive. She gets 30mpg average, and she has a heavy foot. It needed just some minor adjustments to the 78' EFI, and the timing is set to factory spec. It runs fine on 87 without detonation.

If in fact the output is inverted, then it must be in your wiring of the coil circuit. Hear is the MS-II manual page on wiring your coil: http://www.megamanual.com/ms2/vb921.htm

The difference between 3.1ms and 3.6ms will not blow the VB921, especially if you are just idling the motor. You need high RPMs (duty cycle) to get the VB921 hot if all settings are close (I've run a VB921 on the test bench overnight at 7000RPM, and it got quite hot, but never burned up). Chances are, the output is not inverted, so the VB921 is sourcing current through the coil most all of the time. Check your settings and wiring again. If I had an MS-II, I would hook it up in my lab and confirm that the output is inverted with a scope, but all I got is MS-Is. If you turn on the ignition, and don't start the engine, the VB921 should never get hot. If it gets hot when the engine is not running, the output is not inverted.

Yes, idle stop, idle screw, whatever you want to call it. It is how you adjust how much air goes into the engine at idle. Are you sure it is the VB921? You have the spark inverted in your settings (as it should be). The VB921 should be driving the negative terminal of the coil.

Did you adjust the idle screw on the throttle body? Adjust it so that it idles. Then check your timing with a light. it should idle fine at 25deg. The timing in the table for the active bin should match the light. Use the trim in the spark settings to compensate for any error. Once you get the timing and fuel right at idle, you may need to readjust the idle screw.

It will either end up on a 3.1L NA street engine, or a twin turbo 3.1L using some stock RB26DETT turbos I have access to. I'm leaning towards the NA 3.1L. I'm going to try and make the entire engine like Nissan meant to do it that way. I've got a long way to go before it goes on an engine, and then in a car, so bear with me.

Hear are some updated photos of the SU EFI intake I've been working on. It is all smoothed, and ready for bead blast and finishing. Needs the ports opened up a bit, but I will leave that to the guy that does the head. It is a combination of 280ZXT throttle bodies, SU manifolds, and and an EFI manifold. The linkage is all Nissan. I'm working on adjustable throttle rods. The Palnet rail fits nice. I need to make new brackets to hold it down.

It made 185HP at the wheels. Flat tops N47 head mild road race cam header Megasquirt

I just finished a mild L28 race motor with ITM flat tops. So far it has survived the dyno, and close to 250 miles on the track. I'll let everyone know if I have problems.

Give us more information on your setup. Bore, pistons, head, etc. etc.

I think think that saying the stock EFI is junk because of deteriorated connectors, or a bad AFM is not a fair statement. The same could be said about leaking carbs, with deteriorated gaskets, o-rings, bad floats, clogged jets etc. The stock EFI is a great system when in good working condition. Carbs also work great when in good condition. Now when it comes to tuning, both have to be tuned. You can't just slap a carb on a modified engine, and expect it to run right. Same with the stock EFI. But as per my earlier post, you can tune the stock EFI to perform quite well on a MILDLY modified engine. There is no way that the stock EFI can make the power that a set of triples can, but you'd be surprised how much power you can make with a modified stock system. I've tuned a number of modified Z engines with stock EFI by faking out the ECU, and increasing the fuel pressure with very good results. Megasquirt and other programmable units allow precise mixture adjustments at different load and RPM points. With carbs, you can only do so much with fuel and air jets. Most likely you can get the mixture right at full load, and max RPM. Anywhere else in the power band is a crap shoot. I've watched an expert changing air and fuel jets on a a set of Mikunis. Took close to 5 hours to get the mixture right at max RPM and load. It still had a super rich spot at 3000RPM. Not much you can do about that. With programmable EFI you can eliminate those flat spots.

The only way to know for sure what the EFI us doing is to get it on the dyno with a WB O2 sensor. Doesn't matter if it is carb or EFI, you still have to freakin' tune it. Anything else is pure speculation. With the stock EFI you can adjust the AFM, and fake out the coolant sensor with a potentiometer to get the mixture close across the power band. Put an adjustable fuel pressure regulator in there to tune the top end. Once you have the mixture as close as you can get it, start advancing the timing. If the motor has a stock compression ratio (8.something:1), then you should be able to run in the mid 30s in total advance. Don't expect huge power gains by adding a cam to a stock long block. As you noted, it will most likely fall flat on it's face under 3000RPM. Higher compression ratio + performance cam will yield the best power gain.

I find the MS readings to be very accurate. I have a 192F thermostat in there, and it usually reads around 189F.

Ditto on Jon's comments, 200WHP is achievable without head work. I recently built a 0.020" over L28 that makes almost 190WHP. 10:1CR, untouched N47 head, and 460 lift cam. I'm running a conservative timing of 25deg, and power doesn't start dropping off until 6500RPM or so. Running a 6:1 header, ZX intake, 60mm TB and Megasquirt.

HybridZ member Dan Baldwin doing a time trial at NHIS.

Injector size is not important, air-fuel ratio is. So as long as the AFR is around 13-13.5:1 for an NA motor, who cares how big the injectors are. Even the highest performance NA L-series only needs 36lb injectors. Going larger will just have a negative effect on your idle quality. Hear is what I recommend for a modified NA L28 (stock fuel pressure): - Stock CR, mild cam, headers, TB (140-160WHP): stock 18lb/hr - 10:1 CR, medium cam, mild head work, headers, TB (160-200WHP): turbo 26lb/hr - L31, 10:1, hot cam, head work, header, TB (200-260WHP): 36lb

That is an old workhorse of a analog scope. Great scope, especially for $100. You should be able to find a current probe that will work with it. A 0 - 10A range, with a 1:1 ratio (1A = 1V) probe will work fine. You can also use it for setting the proper coil charge time (dwell). All of the scopes made today are digital. Once you get your waveform in the digital domain, the sky is the limit as to what you can do with it. A 100MHz scope is fine for most all automotive work, unless you are debugging an ECU. Real time scopes range in bandwidth from 100MHz to 18 GHz today.