Getting knock at 12 psi of boost

[turbowrenchhead]

I have been working on an 84 gn that is a friend of mine. I pulled the turbo off and ported it to the t/b. I cleaned it up and put a polished elbow and a larger puck in it. I put a used stock dp on it cause his leaked. And we put a piece of pipe in the cat but it was already gutted. Also new Cr42ts plugs and a set of new wires. I set the tps to spec and did a idle reset. I dont think it has anything to do with it but when I put the tlink on it and went for ride he was gettting knock and pegging the stock boost gauge. I backed it off and at 12 psi of boost he was still getting 8 degrees of knock. The MAF numbers are only 160 at WOT. I know that they are spose to be pegged at 255. Can the maf peg at stock type setup? He also has a maf from Jegs witch I dont think is the best thing. Just trying to get some ideas. My next step is to bring my know good maf and put it on. And measure the supply voltage to the maf. He also has a stokc factory rebuilt ECM with a chip from jegs, we tried the stock chip but it did nothing to the maf numbers but lowered the boost even more. What do you guys replace the stock maf when it goes bad, I am lucky cause my orginal still works fine.
Any thoughts are welcomed

 

[TurboRegal84]

CR42TS plugs are a bit cold.....Try to swap them out for CR43TS's gapped at .035....

 

[turbowrenchhead]

I ran 42's just fine in mine with no problems.

 

[FJM568]

Put the 43's in and check the boost with a GOOD aftermarket guage and not the factory one...geez, you ought to know that by now...

Two motors set up roughly the same will not run the same...PERIOD!!! You've got to tune each motor to run it's best with what it's got...His motor could be a fresh rebuild, or a 180k mile motor that is on it's last leg with 40-50% blowby and an injector that isn't firing!!! Just because the setup is nearly the same, doesn't mean it will run the same...

BTW, he may still be overboosting/detonating and the ecm is pulling out timing and boost which will lower your max MAF numbers...As I've mentioned above, if you don't have an aftermarket boost guage hooked up, do it, the factory guage is a POS!!!

With the stock turbo and a K&N filter, he should be able to get close to 255 on the MAF, with higher than stock boost levels, say around 15-16#'s...What is his MAF reading at idle??? What is it with the ign on/engine off??? Don't even bother with measuring supply voltage to the MAF, I don't even think anyone has any specs on what it should be at any level anyway...Just look at TLink and use those MAF numbers...That will tell you more info than anything else...This really isn't rocket science, you just need to look at all available info and find the common denominator(bad or misadjusted sensor, etc) and correct it, and not throw parts at it, hoping that one of them will fix it...

Don't take this post the wrong way, but there seems to be more people with hotairs throwing more and more mods at these cars to get them to run "as fast as" the IC'd cars, when you really don't need that many mods to run low 13s/high 12s...Do the basics and tune, tune, tune...With a stock turbo, injs, Walbro 307 fuel pump, a K&N, an 87 ecm upgrade, and a Jay Carter street chip and about 21# of boost and race gas, I was running hi-13s on street tires with a motor that had a lot of blowby and the wrong head gaskets...Heck, if I had as many mods as a few of the people here has listed for their hotair motor, I would be giving Lee Thompson a run for his money!!! <down off of the soapbox>

Sorry for the rant...

 

[turbowrenchhead]

The guy doesnt want to spend any money on his. His dp leaked and he asked me what to do, I told him to get a atr. No too much money. I then asked if he wanted my old one for 50 bucks. I am not removing my boost gauge just to measure his. And I will have a hard time talking him into changing the plugs again when we just did. I get on the tlink at idle. We got only 160 with the air filter off at wot. Something is not right with the maf numbers I'm sorry. I know my maf is good so I am going to try it and see what happens.

 

[FJM568]

Make a run with the wastegate disconnected so that it won't overboost...Just get out of it before it does Obviously, make sure that the vacuum hoses are all in good shape between the turbo, wastegate, and solenoid and that the Tee is installed the right way...Another way to make sure that it won't overboost is to get a regular vacuum tee without the restriction in it and install it...The car shouldn't make any more than about 10-12 lbs of boost that way...

Well, as for plugs, at $10 tops for the set, and a little time to change them, I don't see why he wouldn't change them...Heck, if they work okay in your car, why not buy him the 43's and trade him for the 42's??? What do they have, maybe a couple of miles on them???

As for the boost guage, tell him that next to upgrading the fuel pump and a scan tool, the boost guage is the next most important thing to have...What are the cheaper Autometer's going for nowdays, $25-30???

 

[FJM568]

Oh yeah, one other thing...Make absolutely sure of what kind of gas he is using...If he is cheap enough not to want to spend money on his car, he is also cheap enough to think that the mid-grade(90-91) octane gas is good enough, too, because he doesn't want to or think that he needs to run the premium(92-93-94) octane gas(what difference would one or two points of octane mean, right??? is what he would say)

 

[EyeTalk2Trees]

...Make absolutely sure of what kind of gas he is using...If he is cheap enough not to want to spend money on his car, he is also cheap enough to think that the mid-grade(90-91) octane gas is good enough, too, because he doesn't want to or think that he needs to run the premium(92-93-94) octane gas

that is so right on the hotair cars. On my 84Gn i have almost the exact set up that FJM568 said could go 13/12s. I don't know about 12's but i could see it run mid to low 13's. In lubbock the best gas i can get (not at a track) is 91, and i question that, in Houston i can get 93. I run it at 12lbs and you can tell a difference, with the 91 it pings @8lbs (90F outside) maybe get to 10-11 on a cool night, with 93 it slams over to 12lbs with no troubles. I'm in college and can barely afford gas alone so i don't buy octane booster every week, I just take it easy, I know it would run better with good gas and just take it easy untill i get to Houston. Not much street action in Lubbock anyways.

Did the car run before the leaking DP at 16-17psi (pegged stock guage) without knocking? If so I'd love to learn that trick!!!