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ECMlink Cooling fans cause rpms to drop drastically

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jamel16

15+ Year Contributor
282
234
Aug 6, 2004
Richmond, Virginia
Good evening fellow tuners, I have an issue I’m trying to sort out. I have two SPAL pusher fans that draw about 15 amps a piece. When they engage or come on it’s makes my rpms drop drastically to almost stalling. The kicker is this happens when I’m running my kelford 272 cams, when I was running stock cams this issue never happened, everything transitioned perfectly. I know vacuum plays a huge part, but there has to be a way to tune around this. Thanks in advance. I also upped my injector battery voltage and that didn’t help.
 
Are the grounds on the car good? I recently upgraded my factory grounds and it helped stabilize the electrical system in the car. Less voltage drop when my spals come on or when the AC kicks on.
 
It sounds like you got an issue with the idle speed controller itself or the adjustment of it. Those things are known to be fineky. Have you had a retune since the cams and or checked for any boost leaks? Did you double check the fan wiring? Sounds like something I've dealt with before in the past.
 
Are the grounds on the car good? I recently upgraded my factory grounds and it helped stabilize the electrical system in the car. Less voltage drop when my spals come on or when the AC kicks on.

Yeah I redid all my grounds, it’s just weird I don’t have this issue with my stock cams
 
It sounds like you got an issue with the idle speed controller itself or the adjustment of it. Those things are known to be fineky. Have you had a retune since the cams and or checked for any boost leaks? Did you double check the fan wiring? Sounds like something I've dealt with before in the past.
Yeah I actually did a boost leak test last night with no leaks. I’m also thinking it’s my idle controller, but it seems correct on link, isc reads 30 and learned idle adjust 144. I might take the fans out and look at the wiring again.
 
Good evening fellow tuners, I have an issue I’m trying to sort out. I have two SPAL pusher fans that draw about 15 amps a piece. When they engage or come on it’s makes my rpms drop drastically to almost stalling. The kicker is this happens when I’m running my kelford 272 cams, when I was running stock cams this issue never happened, everything transitioned perfectly. I know vacuum plays a huge part, but there has to be a way to tune around this. Thanks in advance. I also upped my injector battery voltage and that didn’t help.
Since you mentioned that this happens only with the Kelford cams, if it's true and if we assume everything is as it should be, should try to make the overlap less by adjustable gears and see if it would be better or not. If it would make it better, then the cams are the cause. In that case, you have to compromise something. If you don't want to sacrifice the overlap, then try to raise the idle RPM a little bit to avoid stalling. And look for a point that you can compromise.
 
I think the fact you swapped out your cams is just coincidence that this is happening. I'd be looking more into electrical drain- watch your battery voltage as you turn your fans on and figure that out. My guess would be that if you put your old cams in it would still do it. Something else changed during the cam swap- my guess electrically

I have put some pretty large cams in with very little overlap (-12in/hg at idle) and not gotten such a drastic change in rpms when fans kick on. Have you taken the car for a spin and still noticed this issue?, or is this something youve noticed solely doing idle tuning since the cam swap? Have you given your alternator a chance to really kick in- (revving the motor up a bit after startup)? I know that seems dumb, but I have overlooked simple shit like that before.
 
I think the fact you swapped out your cams is just coincidence that this is happening. I'd be looking more into electrical drain- watch your battery voltage as you turn your fans on and figure that out. My guess would be that if you put your old cams in it would still do it. Something else changed during the cam swap- my guess electrically

I have put some pretty large cams in with very little overlap (-12in/hg at idle) and not gotten such a drastic change in rpms when fans kick on. Have you taken the car for a spin and still noticed this issue?, or is this something youve noticed solely doing idle tuning since the cam swap? Have you given your alternator a chance to really kick in- (revving the motor up a bit after startup)? I know that seems dumb, but I have overlooked simple shit like that before.
Yeah that makes sense also. I’m going to look further on the electrical side. I’m going to pull my cooling fans and double check everything. Maybe my relay is initially bogging it down.
 
@DSMPT
Hiroshi, what idle speed works on your car?
I have it at 950 on my daily 2g.
On 1g, when it still had A/C and when it had some 272 range cams with the stock throttle body and ISC (I don't remember if it was with 1050cc injectors or 1200cc), IIRC I had it at around 1000-1100 rpm. I remember that I was also struggling with stalling since I had a light weight aluminum flywheel. It sometimes wanted to stall when the A/C was ON. Tried many things but the conclusion was to increase the idle RPM a little bit, in my case that was the only thing actually could avoid stalling because a light weight flywheel drops the engine speed quicker. But after I switched to AEM EMS, it almost got solved since it comes a dedicated idle control feature for stalling.

Yeah that makes sense also. I’m going to look further on the electrical side. I’m going to pull my cooling fans and double check everything. Maybe my relay is initially bogging it down.
I just mentioned one of possibilities according to what you mentioned. It doesn't matter if it's an electrical issue or not, make the overlap less would help to have a stable idle at least a little anyways.
 
How about - Fan = electrical load = mechanical load on the alt belt, which could be harder to maintain idle with new cams?

Also, if your electrical load is enough to show a voltage drop, this could affect your how effective your injectors work at idle - maybe play with dead times.
 
I’m going to look further on the electrical side. I’m going to pull my cooling fans and double check everything. Maybe my relay is initially bogging it down.

Could you tell us what you see for voltage when this problem is happening?
I mean you could tell us "Battery" volts from an ECMlink log, or you could tell us what your voltmeter gauge says.

If it comes to tweaking things to minimize the problem, here's something that is super easy and it makes your idle more stable when you are using idle speeds higher than stock: You could flatten out the ignition advance curve in ECMlink, just in the region near idle.
I did mine up to 2500 rpm, and in the first 2 load levels 0.3 and 0.4.
In "View, ECU direct access from log", here's how mine looks. I changed the min octane table the same way.

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If you get into fooling around with the ISC (idle speed controller) and if you are using a 1990 ecu and still have the original 1990 isc in there, then be sure to look at my thread about the 1990 isc which is here:
https://www.dsmtuners.com/threads/1990-isc-motor-–-reverse-polarity-for-new-part.514056/
 
Thanks for the info, when I looked back at the gauge and log, it dropped down to 12.8-13.1. I actually have my timing map setup that way in the idle cells. So I drove a little the other day to pinpoint the issue. This usually happens after I drive in stop and go traffic. Once I’m back at home I let it idle for a few minutes to see if it happens again. This is where it gets weird, the issue becomes intermittent. My next step is to throw my stock cams back in to verify if the issue is still there. I’m also going to give some background on the cams. The cams are original Tomei Poncams 261/261. I had delta cams check them out and they said the cams spec’d out very close to kelford 272.
 
Well, as long as those voltages stay above about 12.5 volts, I don't think that low voltage is the problem.
My car never had any such problems for the years when my logged "Battery" voltage was usually about 12.5 volts at idle.
That was with a pretty old alternator.
Then I got a couple of new alternators and my idle voltage became more like 13.5 to 13.8 volts.
All those volt numbers are with an 1100 rpm idle.

During a time when I had a dead alternator, I did some testing, and as I remember (and from my notes) I was able to determine that when my voltage reading right on the battery terminals (with a multimeter) with the car running was 12.0 volts, it would barely run and would die easy, was basically not driveable.
This was with 3 fans running continuously. Those 3 fans would have a total electrical load pretty similar to your 2 fans.
Anyway, 12.8 to 13.1 is I think not bad enough to be the problem, especially if that is the number you see in a log, because ECMlink "Battery" voltages seem to run a little low compared to what you measure right on the battery terminals.

If it is intermittent, then I start thinking it is likely to be the ISC acting up.
Although when my ISC started to go bad, it was more like I started having very high idle, like 2,000 rpm maybe, and it would be variable all over the place.
I might have had a more minor problem with the ISC for a long time before that - engine dies when you put the clutch in and take your foot off the gas. But I never knew for sure if that was the ISC's fault or something else.
 
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So did a little more research, the same thing happened after I installed the stock cams, it’s just more pronounced with the kelfords. I can actually hear the relay going crazy with the fans on. My solution is to ditch the single 60 amp relay and dedicate a 30 amp relay to each fan. I’m actually going to redo my entire relay panel/ fuse box. I will document this in my build thread.
 
Can't you adjust the voltage offsets to counteract the draw on the system via Link?
 
Yeah I tried that and it was still doing the same thing. I actually read its not optimal to put two high amp fans on one relay. Learn something new everyday
 
I run twin Spals, each has its own relay though.
As a "test", turn on all your accessories and the blower motor on HIGH and see what the engine does. If it acts the same (and mine does), then I would continue to "play" with the voltage offsets until I was for sure that it had no effect. That is what that tab is there for, to compensate for voltage fluctuations.
 
Super easy fix!
 
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