Temporary solution to high hydrocarbon reading for road worthiness test .

So A bit of background about the car , the situations and some possible solutions available .

Car is 2jz gte cefiro ,with a single turbo t88.

Car came mapped for E20 fuel and runs well .

Car is currently set up with a HKS FCON 3.3 .

I am currently doing a mix of this fuel https://vpracingfuels.com/products/c85 with pump fuel 95ron E10 to make a e20 mixture.

I will be getting a modern standalone ECU later this year and running car on our crappy pump fuel, but at the moment I am just trying to complete the road worthiness test for my country as being able to drive the car will accelerate the speed at which I can get the car set up properly .

The car failed on high hydrocarbon reading. The reading was 1002ppm at 3200rpm , the limit is 750ppm .

So I am wondering what my options are to pass this test with what I have available to me at the moment.

Option 1 , Bring car to test with just 95 ron e10 in the tank. could it be possible that the 106 ron petrol in the VP racing fuel caused the high HC reading?

Option 2 , weld in a vband'd racing catalytic converter. the car is currently a straight pipe from the turbo to backbox. in my country this allowed due to the age of the car so long as it can pass emissions. I have a Cat with vbands on another project car . not sure of its spec.

Option 3 , get the HKS software and adjust the fuel table temporally for the test and revert back to the old table once test is complete. Not sure about this idea as it sounds simple but I have no experience at the moment with tuning ECU's

Just wondering what peoples thoughts are here , perhaps it is unreasonable to think any of the above options would work and I should just wait till I can afford the modred ecu / tuner.

Thanks for reading.

Too much HC is an indictor of incomplete combustion. So are you sure your timing is correct and has sufficient advance to complete combustion.

Next, are you sure the fuel mixture is hitting Lambda 1.0 in the test range (probably low-load to cruise at 3200 RPM), if it's too rich, then you could have more HC emissions.

So - I would point to your HKS FCON tuning.

Ok thanks very much David .

I had the same issue with the Nct few years back . A quick and dirty fix that worked for me is to lower the fuel base pressure slightly to get the H.C. in range but at the time I did have access to a H.C. analyser to reference.

After the test I set the fuel pressure back were it was

But like David said tunning the fcon is a better option

Are you sure that you are getting your fuel mixtures right?

If the mixture has a lower-than-tuned ethanol rating, then the same volume of fuel will create a rich mixture. You could mix a stronger concentration of E85, and it will run leaner, possibly getting you through your NCT. It would be good to test with a wideband sensor to see if you are running anywhere close to lambda 1 before testing

Cheers lads ,

I guess I could stick a wideband in the back box and try the fuel pressure idea as well as the fuel mixtures.

Its totally possible that the mix is off , I have been using a concentration calculator to do the mix but I will check over this again to be sure.

One thing I have noticed on other peoples test sheets where they have had the 2 gas tests for older cars is that the tester done the low idle test at 1200 rpm , where as he done mine at 3200rpm , someone mentioned that it was probably the case that he was trying to get the car to pass , would fuel mixtures be linear across all rpm or is it possible that he done the test wrong?

Areas of free revving or next to no load should all really be under closed-loop control.

The higher revs can help 'light' a cat if in place, and also, the higher revs can help mix a bad spray from an injector with the increased air velocity

Thanks Chris

So I have the retest today and unfortunately I haven't come up with a solution to the hi HC as I had many other issues to sort out ( suspension and brake related)

As a last ditch effort to pass the HC test could I run the car 'lean' by adding more 85 than normal? seeing as the car is mapped for e20 would it in theory run 'lean' ?

how bad of an idea is this , the journey to the test center is roughly 15km there and 15km back.

EDIT - sorry I see this is what you said above chris .

Is there a reason you just don't tune it for lower HC (get the mixture right and advance the ignition)? That is really quite simple.

No reason.

That is the plan it's just a time and logistics thing at the moment.

I don't have the know how to do it my self at the moment and not had the time to bring the to a tuner.

As i said this just temporary as having the car road legal would make doing all the permanent work easier for me.

Crappy excuse for just doing it correctly I know 😅