How are you guys dealing with the Stock Tach performance. When I got my Accord 4-5 years ago I noticed that the engine did not seem to rev as high as listed. I went thru all of the basic troubleshooting steps, wired a vtec light to be sure Vtec was kicking in, checked to make sure I had the correct ECU and such. No matter what I did the fuel cut was about 1000 early. I changed out the tach in the cluster with no luck. I ended up wiring up an after market gauge that seems to read more accurately but it does bounce a lot even after installing the filter that was supposed to resolve that. You get what you pay for. Its good enough for me to keep an eye on things. Since then I have been thru MSD coils, 4-5 ignitors, 2-3 distributors, Engine swap, engine wiring harness, new trans, 3 different VSS and I recently even swapped out the whole cluster just in case.


Nothing seems to resolve the issue, its always about 1000rpm low. Well except at idle, seems like the higher the rpm the higher the offset. I have been reading about this for many years and it seems to be a common issue. I have read that you can calibrate the stock tach, I'm going to look into that further. What have you guys done to resolve the issue? I would love to use the stock tach since it is in the best position.

 

I pulled apart one of my spare clusters and it looks like there is only 1 pots switch on the tachometer. I'm thinking I should run a power, ground and test tach wire and hook up the spare gauge and see what happens when I turn the switch. Maybe I can dial it in. The tach works smoothly but just reads low.


I was thinking.. I changed my bulbs to Red LEDs but the color is still a little weak There is a blue coating on the back of the face, I wonder if I can take some acetone and clean that off? Also, the lights are a little dim, I'm thinking maybe I could install some reflectors, like the ones in flashlights around the bulbs to get a little more brightness from the cluster, any thoughts? The other thing... redline is at 6400. Since I have a JDM H23a I wonder what the best way to modify the redline would be. On my old prelude I just busted out the sharpie but I wonder if I can remove some of this red or is it deeply ingrained into the face?

 

As i was looking at my cluster i was thinking about the spare prelude cluster i had sitting here. The Face sizes are pretty much identical and they have the same connectors just spaced a little differently. I think with a little dremel action and i would need to run a few wires and connectors i could make the below happen. The glow faces are just what i have laying around so ill try to get them to work as well.

 

Just a note, i will use the manual face, i have one but its currently installed on the car.

 

I have never seen a stock tach that was 100% accurate over the course of many years and many cars driven/tuned/etc. Never heard of calibrating them either. For me, majority of the time when the ICM was on it's way out it would read low at high rpm or bounce around. I have a separate ignition box now with an ICM delete and my tach still reads wrong so surely there are multiple factors. I'm revving my turbo F20B to 7600rpm and the USDM F22 tach would read about 7k max. I switched to a true SiR tach with the 7400 redline and now it tells me I'm revving to about 8200 lol. I just take the tach reading with a grain of salt and look at the true reading in the engine management.

 

There was a thread on how to fix the tach, but I cannot find it via the search function.

My own tach('95) reads progressively worse. Up to about 1500 its fine, but slows down. Reads 2K @2.5 actual, 3K @ 4K actual and redlines @5K which is ~6250 actual. I've confirmed this by using the tach test port underhood. On 2.2 cars it is a blue with white dots wire near the fuse box. It has a plug on it. This eliminates if it is a Tach issue or the ICM taking a dump.

GM tachs can fail when part of the resistor bank fails. 90's Camaros come to mind. If you could find out the correct values of given parts you could diagnose your own tach issues.

 

I have my aftermarket tach connected to the test port now. I have a 3 gauge pod now and I don't want to add any additional Pods. I plan to add the Wideband so hopefully I can get my tach working and use that spot for the wideband. I don't want to give up my coolant temp or oil pressure gauges. I have been thru quite a few Ignitors so that's not the issue. I think the stock clusters just start to get a little lazy as they age. I was set to go ahead and try using the pots switch to adjust it and see what happens but now I think I'm going to give these prelude cluster parts a chance. I'm feeling pretty lazy and don't want to get out the dremel. I will need to make a trip to harbor freight as well for some wire connectors most likely. I think it will look pretty sweet and hopefully work properly. I just don't know what the condition of these prelude gauges are. I suppose if it get it mocked up and its awesome I can find another good working cluster and swap everything over.


I am still learning this new motor and when I hit the rev limiter around 6k it bugs me. lol

 

My phearable chipped ecu should be
Vtec: 4800
Revlimit: 7800


Its a little hard to tell with one inaccurate gauge and one that does not move smoothly. Feels low to me still, I used to rev my h22a as high as 8500. lol

 

I decided to follow thru and see what happened.
The temp gauge and fuel gauge did not end up lining up. Im not sure if all prelude clusters have the Tach/temp and Speedo/fuel gauges combined but i ended up cutting them apart. Im pretty sure that kills the glow face, not the end of the world.
Here is a pic before i cut them. You can see they just dont line up.


I did alot of cutting to fit the tach into place, i was also trying to fit the temp gauge and routing for the glow gauges so i did more cutting than was necessary. I will still need to wire up the tach but that wont be a big deal. The speedo uses the factory connections and mounting spot. I did end up shaving some of the mounts for better fitment. I tried to change the needle on the temp sensor with the red one but that gave me alot of trouble so i gave up. Here is where i am now.


I think i can order a set of white faces for both the accord and prelude and everything should match up.

 

Had the same issue on my 92 CX. An Omni tach later and I'm GTG.

 

I checked an EG cluster I have laying around and the tach is smaller. Question for you, was there a lot of overlay with the gauge face and front face of the cluster? Looking at the pictures of the Omni it looks like there is a good inch being covered.




Using the Prelude parts looks like a little more of a pain, I cant find a standard white face or black face to put on it. They only seem to sell the glow gauges and once I cut them they wont work at night anymore, I believe. I think I need a stock prelude gauge to make it work and look decent. I can do the black faces and maybe add some fancy rings to the cluster.


I think I'm going to test the calibration, that would be a free fix to the problem.

 

How is it you are determining exactly how much it's off ?

Head to a tuner. Have them hook up their ecu. Check how accurate your tach is. Keep in mind the very first big line after 0 is 500 not 200.

 

I have the same problem with mine. The way I calculate the error is to look at the speedo. It matches the speed on my Garmin, so it seems to be correct. Then looking at the gearing, I determine what the rpm's should be at that speed. The tach is off by about 500 or 600 rpm's at 70mph. As speed increases, the error gets greater. The rev limiter will kick in at around 5200 rpm's. It used to be that the error was less when the lights were on and the alternator was having to produce more voltage, so I thought the problem was the tach's inability to sense the correct voltage from the distributor. I have a JDM tach with about 35,000 miles on it but I haven't yet put it in the car.

 

I tested out the Prelude tach and Speedo last week when i did my wideband install and they did not work. I think the gauges were just bad, the needles are very stiff and do not drop back to 0. Ill keep my eyes out for another prelude cluster and give it another shot since i spent a few hours dremeling out my spare cluster. I didn't like the white face glow gauges(that i cut and broke anyway) there was a little light that came thru around the tachometer but i think I'm going to order some of those fancy chrome rings that will cover that up.

Anyone have any input on why the tach and speedo didn't work? The F-series and H-Series are pretty much identical as far as wiring goes so i would assume they would be compatible. The speedo even lined up perfectly with the 4 connections to the circuit board.

Just a note, i have an aftermarket tach as well which lines up perfectly with Vtec engagement and fuel cut. Its definitely the cluster or another unknown component that's causing low rpm readings. I cant imagine what else it could be, there are many many posts with this issue, i think the stock tachometers are just past their expire date. haha. I have changed out pretty much everything except the fuse boxes and internal wiring harness and it has never improved. I get an accurate signal from the test port that my aftermarket tach is connected to.

 

Connect a scanner and see what the RPM says on the scanner.