4AGE Silvertop Lean and Pinging?

[sloth]

Car - 1983 AE86 (SR5)

motor - 4AGE 20v Silvertop (controlled by Link G4 Storm ECU)

use - Daily Drive

problem - There is a ticking noise coming from the engine around 3000RPM - 3800RPM (usually in 3rd gear) when the car is under load. I think there is also a slight loss of power.

occurs/started when - I noticed it not long after I first got the car back from the mechanic after the engine had been installed. When I first started driving the car I always kept the revs relatively high, it was only when I started trying to drive a little more "sedately" that I noticed the noise and (I think) a slight loss of power. The noise seems to be most apparent in 3rd gear when I am accelerating and haven't stretched 2nd out, when it gets to around 4000RPM the noise disappears and the car seems to accelerate better.

personal situation - The Silvtertop engine was fully installed by a mechanic in Melbourne and tuned by AVO Turboworld in Cheltenham. When I picked the car up everything was supposed to be sorted, and it had been dyno tuned earlier that week. Comparatively (to my KE55) the car had more power, but the dyno results said it made 67.8 rwkw (which I thought was a little low, expecting around 80 - 95). My mechanic didn't mention any problems with the car or tune.

At first it all seemed fine, but (as previously mentioned) after a while I noticed a ticking noise when accelerating at around 3000RPM. I thought nothing of it and was simply going to have it looked at at the next service. I've been driving the car now for around 4 or 5 months with the performance of the car being the same as the day I picked it up. The only problem has been that the fuel pressure switch on the engine broke and needed to be replaced. The car was put on the dyno (a different one from the original run) about 2 months ago and made 67.3 rwkw (approximately the same as the original run). The tech running the dyno mentioned that the results indicated it could be running a little lean and the the air/fuel mixture could be adjusted.

I took a friend for a drive in the car last week and pointed out the ticking noise. He was slightly concerned and after a little googling he self diagnosed it as pinging. I did a little googling myself and came to the same conclusion. (Here are some of the sorts of sites that seem to fit with it ).

I had a look at some youtube videos of cars that were apparently pinging (had knock) last night and again this morning, some seem to make the same sound, others it is more of a thump. In most cases though they are getting the ticking sound even at idle.

Most things I've read state that if you are experiencing pinging you should increase the octane of the fuel you use, as a caring 86 owner I've been using 98 since I got the car (the dyno tune though was performed with the petrol that was in the tank before the engine change, which would just be regular).

Does what I'm experiencing sound like pinging? Can I still continue to drive the car until I get a chance to have it looked at by a mechanic (I'll be doing this ASAP, but it's a little difficult at the moment as I'm rather poor and use the car to get to and from work)?

In case it helps I've attached the results of the two dyno sessions and a screenshot of the fuel table from the ECU. Any advice would be appreciated. I'm not a mechanic and (while I consider myself rather smart) I have no idea when it comes to anything mechanical or electrical.

[Sam-Q]

my silvertop engine has an airbox and under certain throttle oppenings makes a ticking noise which I know for sure isn't detonation even though it very much sounds like it at times

[xero]

taking a wild stab in the dark here but...

looking at your dyno graphs, specifically the AFR's, the first one looks a fair bit rich and the second one (the ESP graph) has the AFR's pretty decent in what looks to be the correct mixtures.


what it think might be the issue with your car is the VVT solonoid being fucked/gunked up/not wired correctly.
the ticking your hearing could the VVT trying to engage but not working.

do you notice a change in the way the car revs above 6000rpm or at least a increase in power after 6000rpm?

again looking at your graphs it doesnt seem to show that the VVT is not kicking in (y0!) and your only running on the standard cam lobes not the fancy VVT ones.
my 16v power curve looks similar (no VVT) and doesnt have the slight increase in power after 6000rpm.








wheres sam when you need him... or ant for that matter.

EDIT: ignore the little bit above.

[sloth]

While driving to work today I watched the tacho a lot closer and noticed that the ticking noise seems to start a bit earlier than I thought (around 2200-2300 RPM), which (looking at the dyno chat with the VVT and non-VVT runs) is about where the VVT kicks in (y0!). Makes me think it is something VVT related as you said xero.

[KENut]

Does it change depending on how much throttle you give it?

I'm not a tuner obviously but
1: looks like its lean at <10% throttle
2; theres a hole at 60-70% throttle (low RPM)

[Anthony]

Has the VVT solenoid output been setup as a slow PWM output and not static, or something like that. So many possibilities. I will say you have to try fairly hard to make a 20V rattle like that, so surely it's going to be something silly.

[Jonny Rochester]

My 20v may have a similar rattle or knock at about 3000rpm. It happens when the motor is making it's most initial torque. It is something silly, it is my aftermarket trumpets (or No. 4 trumpet) hitting the brake booster, but only under acceleration due to give in the engine mounts.

Some other tips on making power (it should be more like 90rwkw).
Double check cam belt timing, confirm ignition timing with a light.
Make sure your AFR is around 12.5:1 when the throttles are open doing a power run, or between 12 and 13.5.
Take all your air filters off while on the dyno, especialy oil/foam socks.
Make sure your ignition timing is up around 35 degrees at 6000rpm with the throttles open.
Fill out your fuel and ignition maps right up to 9000rpm. Even if you don't intend to drive there, the motor may go there at times and you want the ECU to give some roughly OK settings. Even if they are not "tuned" points, have a look and see that they make some sort of sence.
If your not sure about VVT, just disconnect it for at least one of the dyno runs.
Raise the rev limit to around 8500rpm. Take it closer to that on the dyno and see what happens. The motor is made for it.

If none of that works, you need a rebuild.

[sloth]

@KETNut
I can see what you mean with the hole, little bit weird. You'll have to check out the 86 soon, I'm sure there has to be a cruise, hillclimb or event coming up that we will both be at. I don't think any of the Canberra Rollaclub guys have actually seen it yet (getting a little off topic).

@ Johnny
Those dyno runs were all done were all done with the socks on.
It's due for a new cam belt at it's next service (which is about now), so I'll make sure the timing gets looked at then.
My mechanic also blames the tyres for the lack of power, as there isn't a lot of grip.
I was a little surprised the rev limit was set so low (it varies based on the engine temp, but the highest it goes is 8100).
I'm pretty sure the noise I'm hearing isn't something hitting something else, but I'm beginning to think it's probably something equally stupid or simple (something wrong with the way the VVT is connected or just gunk in the gear/cam as people have mentioned).

[Jonny Rochester]

Save up some money and take it to a different tuner. Foam socks are well known for robbing power. A 1.6 litre N/A should not be spinning the wheels on the dyno, even with old tyres. Some tuners don't even bother strapping them down.

[Frak]

Bloody 20v's, as many know I have been an advocate for many many years, lately been spending an unsual amount of time with modified ones, swapping cams, head work etc, they don't act like a typical engine, we make changes, it doesn't respond how a 16v would or normal engine(advancing/retarding cams etc) we just laugh and say "that's a 20 valver" seriously, this is an odd engine to modify. I know people will say an engine is an engine, but over the years I have spent alot of time on these engines and have some theories as to why they respond the way they do and why they act like they do.

had an unusual problem with one the other night, have been messing with different header lengths/diameters. gave it a run, had this unusually lean patch from 3500rpm to 5000rpm, turned off vvt just to see if it was affecting it, it was but HUGE loss of torque but a/f was now nice. anyway turned vvt back on in this area, started adding fuel, still lean, anyway it got to a point where it was lean then just adding a bee's dick more(not very well hung bee either!) and instantly very rich, it was amazing! it was the headers, just happened to be when the negative wave arrived back at the open exhaust/intake valve, changed header length and altered the a/f ratio. Seriously these things are all over the place when it comes to power outputs, the BT's seem to be more consistant, but ST's bloody hell, they vary so much!! (Iknow there is early and late ST)

Oh another thing I found the other night whilst swapping cams out of 2 late ST engines(what I call second gen ST), the cam phasers located the intake cam in different postion, one gave 0/70vvt off, 30/40 vvt on, the other gave 10/60vvt off, 40/30vvt on, the phasers looked exactly the same, did not looked modified. What has anyone else found?