RETed

No!
It's be thoroughly documented that ALL the FC NA's run rich already.
Running a fuel computer to lean out the RPM ranges will easily increase power.

Putting that resistor to fool the air temp sensor will just supress more power, since it's running even richer.


-Ted

Icemark

100K is radically too high, and will put the ECU into a fault mode on that wire thinking that the sensor is busted.

7.5K would be the absolute highest you would want to go, with a 4.7k much better because then the sensor would still work (just be about 50F cooler in reporting).

Syonyk

Did anyone read my theories on how it works? I'm pretty sure the air density correction (and therefore fuel delivery) is controlled by the sensor in the airflow meter. If ambient air temperature is 70F, the amount of air pulled in at a given AFM opening is the same, regardless of the actual temperature going into the intake ports.

Also, in the other thread (linked in one of my posts), someone recorded a 7HP dyno gain from this. It's not 20HP, but it's still a respectable amount. I agree entirely that the NAs run rich already, and adding fuel will reduce power output. So, to get a 7HP gain (which I would say is probably large enough to be outside the realm of random noise, especially considering everyone believes the power output should drop), something has to be happening.

I'll have more data later tonight. I'm planning to run to Radio Shack and snag some resistors. Right now, my SAFC-II is tuned to run the engine slightly lean of stoich in normal highway cruising (I disconnected the O2 sensor input from the ECU, so it stays in open loop mode for now). I can monitor the narrowband O2 sensor output and see roughly what the fuel mixture is doing. If, in fact, this mod does increase the fuel delivery, I'll be able to determine this based on the O2 sensor output. I'm not convinced that the upper intake manifold sensor does much, if anything with fuel delivery, but that it is used mostly for timing advance.

Short of a timing light on a dyno, is there any good way to determine what the actual advance is under load?

-=Russ=-

Syonyk

Are you discussing S4 or S5?

According to the S4 FSM (Page 4A-81), the resistance of this sensor should be as follows:

20C/68F: 41.5 +/- 4.15 kOhm
50C/122F: 11.85 +/- 1.19 kOhm
85C/185F: 3.5 +/- 0.35 kOhm

If you put a 7.5kOhm resistor in, you'll be telling the engine that the intake air is somewhere around 70C, which kind of defeats the purpose.

100kOhm would be a reasonable value for sub-zero temperature reporting. I need to head to work, but in another thread a while back, someone generated a quadratic formula for this sensor based on the FSM data. I'll dig it up in an hour or two.

-=Russ=-

rxse7en

This "mod" + the leafblower supercharger + AFM gear mod + the Tornado + a dyno would all make for a good story in RXTuner. What were some of those other suspect mods?

gkarmadi

iTrader: (20)

the tornado???...its a joke...i had it in my car...didnt do a damn thing....

rxse7en

Of course it's a joke that would be the point of the article My personal favorite has been the electric leafblower supercharger. I'm surprised it hasn't popped up this year.

B

RETed

I'd really like to see proof of that.
Variables such as water temp cause easily cause power deviations like that.

If all things are kept constant, I would highly doubt an NA would gain anything more than 1hp just by fooling the air temp sensor...



-Ted

Syonyk

It depends on what that particular sensor is doing. I see no reason why it would affect fuel delivery much, if at all. However, it would be in a perfect place to be able to adjust timing, and I think we can all agree that the NA '7s will gain a bit of power from advanced timing. My belief is that this mod prevents the ECU from retarding timing at higher intake air temperatures. This also would explain why on eBay they're not sold for turbo vehicles - advance timing on a turbo, hit some good boost, pop an apex seal. The FC ECUs are incredibly conservative with fuel delivery, and apparently timing as well (from the gains seen by advancing the timing).

As I said, I'll get numbers later tonight with regards to fuel delivery.

-=Russ=-

Icemark

No I am basing it on the AFM, because the dynamic chamber temp sensor does next to nothing.

You can check that with a timing light yourself (I have). The dynamic chamber temp sensor is used for hot start. Not air density.

Syonyk

*shakes head* These resistor modules plug into the dynamic chamber temperature sensor readout, not the airflow meter.

I'm basing this information on this thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/intake-chip-433244/ Someone who purchased one took pictures of where it gets installed. It definitely goes to the dynamic chamber sensor.

At this point, we have a few people over in the other thread saying that this does work, and one reported dyno gain. We have here a lot of people saying it's junk based on theory. Even at Radio Shack, a pack of 100kOhm resistors is cheap. Can some people with heavily instrumented cars (wideband, EGT probe) with the stock ECU try this out? Fuel delivery changes would instantly show up on the wideband, and I believe timing changes would show up on the EGT probe. To do a slightly more scientific test, get a pack of 2-5kOhm resistors as well to test with the engine being told that the intake air is really hot. If, indeed, the dynamic chamber temperature sensor is used for nothing other than hot start, there won't be any difference between the two resistors in exhaust-side readouts.

-=Russ=-

Icemark

, it would be BS, I have tested it myself
No, I say its junk off of actually testing. I have personally run dyno tests on resistors on both the dynamic and AFM. The AFM change with a 4.7k resistor is the only thing that showed any gains (typically 2 HP on a dyno jet).

Yet a 50k 75K or 120k resistor on the dynamic chamber did doo doo.

I even sold resistors on my online store for a while to debunk the Ebay BS, and this is why I did the testing.

So, I am extreamly skeptical that there are any gains that anyone found on any changes to the dynamic chamber.


But prove it for yourself, go check timing with and without a resistor in there. Go spend some dyno time. I have. So saying that :
is pretty much BS itself, and sounds like you are basing it all on theory.

jhammons01

Icemark, I didn't see where you 'said' that you tested it before on the Dyno and had actual results. I bet Syonyk didn't either.

You pretty much proved your point after you said that you already tested it on the Dyno......which is what the thread (discussion) needed. Thanks

Syonyk

Fair enough. I didn't realize you had done the extensive testing.

What kind of ambient air temperatures were you running in when the 4.7kOhm on the AFM showed the changes?

-=Russ=-

mrb455

I got one from Icemark for my 88 fc and noticed a small increase in power, also my 7 runs a very cool temp so I had no knock problems.