Knock sensor blown after dyno

[mlimin]

My car is AT with 5.5 psi pulley supercharge, greddy evo. after I dyno tuned my car (I have SAFC) the check engine light (CEL) is on. During the dyno, the tuner told me, seems like the ecu retard the timing around 6000 rpm. But me and him have no clue at all what happen. The tuner not believe that the knock sensor blown because he lean the fuel too much. I have reset the ecu 3 times, set the fuel ratio back to original, but the CEL still show up. If the CEL light up, I can feel the ecu retard the timing.So I am pretty sure I have blow my knock sensor(OBD tool show I only blow knock sensor on bank#2). toyota want to charge me $140 for the sensor. I have the 5.5 psi pulley for over a year and never have any problem. My question are:

1. with smaller pulley, when you dyno tune the car, do we suppose to lean or rich the fuel mixture? here is the setting on my SAFC:
Hi throttle:
1000 to 3000 RPM => -8%
4000 rpm=> -7%
5000 rpm=> -5%
>6000rpm=> +5%

2. how hard is it to replace the knock sensor by myself? do I have to take off the supercharge to reach the sensor?does anyone have the diagram? or maybe someone can write DIY.

Thanks

[cdssolara]

Welcome to the club of Solara owners who have blown their knock sensors. In my case, it's happened twice; once was at the dyno, like you. Sensor #2 seems to be the primary culprit. Dynos are tough on engines. In your case, though, it seems that your S-AFC settings are at least partly to blame.

From the tuning info that you posted it would seem like you're way too lean. Do you know what the Air/Fuel ratio was? Why did you want to adjust your fuel downward with the S-AFC? With your 5.5 psi pulley, you're forcing more air into the engine, so consequently you need more fuel. The settings that you're showing, except at the extreme high end, reduce the fuel. It's no wonder you blew the sensor.

Replacing the knock sensors requires removing the supercharger, unfortunately. You might want to get a new harness for the knock sensor, as well.

[JoeB]

mlimin, I agree with cdssolara, it sounds like your air/fuel settings on the S-AFC were way too lean. Many people have had problems with their knock sensors after upgrading to a smaller pulley on their sc. It makes sense if you think about it. Why would TRD make a sc that only boosted to 4psi and they cut the boost on the low end. The answers are in this post http://www.zer0.info/solaraguy/viewtopic.php?t=6541 . You need the fuel supplied to keep up with the air you are adding in. 4psi on an sc is laughable on other applications. -JoeB

[Mudd]

Explain to me how one can just "blow" a knock sensor? I've been dealing with turbocharged engines with knock sensors for years now. I run over 1.5bar (22psi) on pump gas in my other car. I've yet to see a "blown" knock sensor.

It sounds to me that the knock sensor is doing it's job. Your car's detonating, probably from lack of fuel, and yanking timing. That's what it's supposed to do. My guess is you need more fuel, which seems to be a big debate on these forums. When you start adding boost, the first thing you do is add the fuel to keep up with it. That's what an AFC is designed for, so you can run more fuel at certain RPMs (where the car needs it), and less at others (say like under idle or light load with a big injuector and fuel pump, where you pull some fuel).

That's also a HUGE gap from 5000-6000 RPM in your AFC setting. You're going +5% to a 10% swing at 6000 RPM. You may well be running at 100% injector duty cycle (time for new injectors) - that causes your engine to knock as well. That's probably also the reason for your CEL. At open loop (WOT), it's maxing out, and it's not supposed to do that, so the ECU freaks and activates the knock sensor.

Do these cars run extremely rich from the factory? Is that why you're pulling fuel at lower RPM settings? I'd start by returning all your settings to at LEAST 0% at high throttle, and start slowly adding fuel. The dyno would be the place to do this, since you can see real results there. not the "seat of the pants" variety (aka -Honda power).

You may want to start looking on other boards, where people have been supercharging for a long time, and see what they're experiencing. I'd suggest some of the Mustang boards, or even the Honda boards. Alot of the supercharger manufacturers have forums right on their websites.

[cdssolara]

I'm not sure that I can explain exactly how the knock sensors are blown. You're right about the fact that they are just doing their jobs. However, once you get a Check Engine light with a knock sensor malfunction message, it just seems that the knock sensor becomes extremely sensitive and trips the CE light constantly after that. I see it happen now whenever I go over 4000 rpms. Until it blew on the dyno, I had gone to over 5000 rpm with no problem.

The first time I had this problem, it was with the #2 sensor, which I replaced. Once it was replaced, the CE light didn't come on again until I blew the #1 sensor on the dyno. A few people have speculated that the replacement sensors are less sensitive than the OE units. I can't be sure that's the case, but I haven't had any problem with the #2 sensor since it was replaced, even on the dyno runs.

I don't understand why the first poster cut back on the fuel at lower rpm. If anything, you need more fuel, although it may not be necessary below 3000 rpm. Also, the S-AFC can not adjust the fuel upward enough at high boost and high rpm unless there are enhancements to the fuel delivery system. I was running stock injectors during my last dyno and S-AFC adjustments over +25% had no effect at all.

The TRD supercharger for our car was only meant for low boost. TRD never attempted to do anything for more boost, or at least they weren't successful at it. It seems to be due to the whole fuel delivery system in these cars. People have been trying to figure out solutions on their own. Ericsol has solved some of the problems by going to a Split Second unit that can adjust both fuel and timing. Now Gadget has come up with a system that seems to work with the supercharger for the 3.4 liter truck engines. He's now trying to make it work for our cars. Check out the thread that JoeB referenced in his post.

[mlimin]

Thanks alot for a quick replay, I have just talk to toyota today, they want to charge the labor it self for $690 for 9 hrs job, but there is a local shop here they will only charge $190 for 2.9 hrs job.

The guy that dyno my car just don;t want to admit his mistake, he just keep blaming on the knock sensor.

The reason I leaned out the fuel mixture is because I don;t understand about the safc and the tuner is the one that did all of the adjustment. He just show me that "we want to have a flat fuel curve". So I just trust him. I pay him $85 to gain more power ends up spending $600 for my knock sensor. I never have any problem with the 5.5 psi pulley until I dyno tuned the car. I run on 92 gas. I guess it just not my day .I am thinking to just replace 2 knock sensor at the same time, since the labor is quite expensive. But is it necessary to replace the harness?

What will happen if I am not replacing the knock sensor?



Masri

[cdssolara]

Without going in for the dynotune, you probably could have got away with running your 5.5 psi pulley on 92 octane gas for quite awhile without any problems. The dynotune is pretty hard on engines. A lot people have blown their sensors during dyno runs.

That's the problem with having someone dyno the car who doesn't completely understand what you're trying to do. Most places haven't seen Solaras come in for a dynotune. This whole issue of trying to maximize power with higher than 4 psi of boost has been a much discussed problem on this and other Camry/Solara boards for the last couple of years. This engine was not designed to be a high performance engine, so people have had to upgrade other areas in order to deal with the higher boost. In addition, since there are no chip upgrades for this engine, we've also had to resort to adding mods that alter the signals being received by the ECU so that it doesn't go into "self-preservation" mode and retard timing. Some of these methods have been successful, others not so much. Bottom line, it's a complex process, and some guy at a dyno shop is not going to know, or care, about the experimental nature of our upgrades.

If you go to the the place that is only charging $190 for the knock sensor replacement, do they know that you have a supercharger that will have to be removed and then replaced? Have they worked with a TRD/Magnusen supercharger before? That seems like a pretty low charge.

If you don't replace the knock sensor, you will probably have the same problems I'm now experiencing. Once the CE light goes off, the car will feel a lot better, but it won't have the power it should. I think there is still some timing retard going on. When you really get on the gas, the CE light will come on again, and the engine will go into serious timing retard. This process will repeat itself until you replace the sensor. It's not a particularly satisfying driving experience, to say the least.

Based on my experience, I would recommend replacing both knock sensors. When I blew the #2 sensor, I only replaced that one. I then blew the #1 sensor later. As I said in my earlier post, it seems like the replacement sensors are less sensitive than the OE units. I wish that I had replaced both of mine at the same time. I will be replacing my #1 sensor soon, when I add higher flow injectors and the JPP headers and exhaust.

I don't know if the harnesses really need to be replaced. One of the techs at a local Toyota shop told me that the originals tend to get damaged easily during the replacement of the knock sensor and just replacing the whole unit is safer. Again, that came from Toyota, so take it for what it's worth.

[mlimin]

Thanks alot for the info cdssolara, so how much did you pay for the labor itself? and how much did u pay for the knock sensor?


Thanks
Masri

[cdssolara]

Thanks alot for the info cdssolara, so how much did you pay for the labor itself? and how much did u pay for the knock sensor?


Thanks
Masri

The replacement of the knock sensor was just part of the process when I had new cylinder heads installed last summer, so I don't have an actual charge for just that job. Toyota will charge me $600-$700 to do the job, so I will be looking elsewhere to get this one replaced. I can't imagine any shop charging less than $400 because of the time involved in removing and then replacing the supercharger. Blowing knock sensors is an expensive proposition when you have the supercharger. I don't want to have to do it again. By the way, when you have the supercharger off, you might think about getting cooler spark plugs and possibly upgraded spark plug wires. Oh, I think I paid around $150 for my new knock sensor. You might be able to get them cheaper online.

[mlimin]

I do have the iridium spark plug, anyone know how longt that thing will last? is necessary to upgrade spark plug wire?

[Yanks0114]

I do have the iridium spark plug, anyone know how longt that thing will last? is necessary to upgrade spark plug wire?

They'll last 30k miles. It is not necessary to do the wires, but its worth considering. Its more for peace of mind and looks

[mlimin]

somehow this morning my CEL is off. When your knock sensor is bad, is the CEL will keep on and off like that?

I also have found, the knocking is around 2300 RPM which is never happen before. I am thinking maybe I can add more fuel around that rpm range to prevent knocking. Do you guys think this will work?

[cdssolara]

somehow this morning my CEL is off. When your knock sensor is bad, is the CEL will keep on and off like that?

I also have found, the knocking is around 2300 RPM which is never happen before. I am thinking maybe I can add more fuel around that rpm range to prevent knocking. Do you guys think this will work?

Yes, the CEL will turn off after a few days. I'll bet if you floor it a couple of times, it will come on again and the timing will be seriously retarded for awhile. I've gone through this scenario before.

Are your S-AFC settings still the same as what you described in your earlier post? If so, adjusting the settings to positive adjustments will probably help. At 2000 rpm, you shouldn't need much additional fuel, but you can step it up after 3000. In my experience, any adjustments over +25 don't do you any good if you have stock injectors. No matter how much you fool the ECU, the fuel system can't provide enough fuel to make that kind of compensation.

[mlimin]

right now I set everything to zero. But my concern is, why my engine will knock even I set everything back to original (The CEL is not light up at the beginning)?

[SC V6]

once the knock sensors blow once, they will until u replace them, because they are crap.. thast about it
later
Scott