AFM adjustment for more fuel

[Guest bastaad525]

heh on every EFI Z I've owned if you disconnect the coolant or head temp sensors the car dies within moments, whether the car is warmed up or not.

 

 

To anyone considering having a high compression or other performance n/a motor built (note, I say "having it built" if you're building yourself, disregard this), please take some time and really think about the invesment you're about to make. I've been down this road... and have kicked myself more than a few times.

 

After spending somewhere around $4-5k on building an N/A motor (I'm counting everything involved here, including intakes, fuel systems, exhaust, etc. not just having the motor built) and only putting about 160hp to the wheels and 160 ft lbs, I was pretty dissapointed. Even when I took that motor out of my 3,000lb ZX and put it into a 2300lb 240, the performance was short of impressive... cant speak for everyone, but to me, 0-60 in close to seven seconds and a 15 second 1/4 mile time were NOT fast. And I had pretty much maxed the potential of that motor, with only three (expensive) options left to me to really get more power out of it: 1. Tripple carbs, 2. Make it a stroker, 3. Lots of head work. Did I mention that any of those three options are pretty expensive? And only doing at least two out of the three of them would have really resulted in any great power gains and got me more than 200hp at the wheels, IMO. So... consider your options. A turbo motor can be had and installed for the same price range (I did a turbo swap and rebuilt the turbo motor for total about $5k, now putting down 200hp and 234 ft lbs). A very basic carbed V8 swap can also be had for around that cost though typically ends up costing a bit more than that. Either option will get you much more power, much more easily and quickly. If you REALLY want a 'fast' car (of course, this depends on what you're definition of 'fast' is certainly some people would have been more than happy with that 15 second 1/4 mile) consider your options and save yourself some time and money... or just kick yourself again and again like I do

[Scottie-GNZ]

Having owned both makes I can honestly say the I will always have a Z and I may never own another P-Wagen. Parts are drastically!!! expensive and the cars are harder to work on than the Zs. Not much faster than a z in stock form the 911 also has an interesting added entertainment feature- Trailing Throttle Oversteer. Gauranteed to terrify both the passenger and the driver for years to come.

No argument about the parts being expensive but if the car is properly maintained they are virtually indestructible. Hopefully you are not trying to compare how most people maintain a Z to how a 911 should be maintained.

 

A 911 not much faster than a stock Z? You must be joking!!!! What kind of 911 did you own, a '69 2.0L 911T? :D

 

Sorry, did not mean to hijack this thread but had to respond to those comments.

[tec280zx]

Any of you mess around with Toluene with your high comp/boost motors? I've gotten pretty good results with it on my 10:1 motor.

[Guest SHaq]

Need to go look at my car, cold and dark out there now. I did it years ago and cannot remember. What is range on your pot, it should be 1-1000ohms. 15 ohms per turn doesn't sound correct- more like 100 per turn on mine. I will look at car tomarrow and repost but you should be able to figure it out with a DVOM - Put it on 2k Ohms scale- attach leads to two of the little post-see if meter reading changes as you turn screw. Change leads around untill you find the adjustable set. 1 of the post is usually a reference and will not be used in this application. It is also possible to just use a normal resistor ( I would start with a 300 ohm one) but is not adjustable.

 

I am running into this problem now after boosting CR and am wondering if it is possible to disconnect the CTS altogether and lean out the AFM and/or decrease fuel pressure with the AFPR? It seems it would be a bit easier. Will it run with the CTS totally disconnected or must there be a resistance reading going to the ECU?

 

I have the fuel pressure raised for now, but would rather increase the duty cycle and thereby reduce the strain on the stock fuel pump and fuel lines.

 

Any ideas???

[Guest jjohart]

I hate to chime in with my own agenda, as I have posted sagas elsewhere, but I continue to have warm restart/idle issues with my I/C'd 83 280ZXT. I just picked up the car from my local mechanic's last best ditch stock intervention, replacing the injectors (one was said to have leaked, but all the old ones measured 2.5 ohms). Of course the car is stalling again as soon as I've driven enough and then let it sit (engine off) for 5-10mins.

I guess I need a little more general help. It sure would be nice if some of the educated voices on THIS thread might provide a PICTURES guide and home installation kit for doing this "small" AFM mod, since I find the descriptions of resistors and opening up and tweaking springs/screws to be quite overwhelming. That said, I appear to have three choices:

1. Take the car to a recommended (Paul-Avalon Racing in NH said see George at Team Nissan) Nissan dealer, pay through the nose for an ECU "consult", hope he doesn't blame it all on the intercooler (this problem was present, though less evident prior to I/C), and PERHAPS he might have a few ideas...but then, he ain't likely to be pushing aftermarket parts and installation, much less fine tuning.

2. Find a "race shop" in the area that can sell me up quick on regulators, etc, but may not really give a hoot about fine tuning out this problem, much less the inversion of a Nissan dealer..in that they sure as hell won't be calling up the Nissan dealer next door to help poor John's 20 year old Z diagnosis out!

3. There's only one old-timer mechanic I know of who runs a Z repair shop, Mike McGuiness in Maryland, and that is a 7 hour drive. He may be versed more in the stock aspects of the problem than the aftermarket, but I've already had fuel pressure checks (ok), checked ignition/vacuum/wires/plugs/injectors...I dunno what he can accomplish, but I guess the 4th choice would be better but impossible....i.e make it out to California/Texas with my Z, where all the gurus online here draw their successes from!

Well, if anyone's a traveling Z mechanic, I'll put up room board etc +, if you can tune my Z's bad restarting out of Natick, Mass-my whereabouts.

I am pretty sure this problem is going to intensify in the summer months!

Suggestions as to what kind of help to seek appreciated, per #'s above!

John