AnthonyPenn313

So first off I searched and found pretty much nothing on my topic so I signed up here and see if this community can help!

So I recently bought a 92 hatch fully build 700+ hp.. I know what I'm doing with it and the what not's but long story short.

-recently I just noticed a thunk or knock when the idle dips... on this hatch it seems to always dip when I left off the gas in a neutral position (in neutral or push in the clutch)

- The dip isn't what bothers me, its the knock or thunk sound it makes. I'm on 17 LBS to learn how to drive the car not 35+ on what the car is tuned for. I opened the hood played with the throttle a little and could not hear the sound. It's only in the car when I here it and it does this every time.

-So even idling.. lets say I tap the gas and it revs to 3k. When it falls down it goes to about 600rpm and levels it way up to 1100. BUT on its way down the thunk or knock happens at about 1300.. and it sounds like its comming from the front of the car.

- To me it almost sounds like something might be vibrating or hitting something but for it to happen every time at the same rpm has got me wondering what it is?


So this is my intro post to the forums owned the car for about a week now and drivin it 400 miles. only really boosted it about 5 times tbh.

All help is appreciated. Thanks!

azzazel_9

if the car is tuned for 35lbs and you're running it at 17lbs that your problem im guessing.

AnthonyPenn313

theres 2 settings one is waste gate pressure and the second is 38lbs

B_Swapped93

I know this car(this is mine) is N/A but it sound like a prob I had

emergencybm

iTrader: (1)

^^^so what was the solution lol

B_Swapped93

We never found it 100%. the map was reading high on idle thus dumping lots more fuel then needed. so I suspect that had something to do with it doesn't do that any more but will do it every now and then on a cold start morning.

jbpnoman

That has nothing to do with his problem, and there's absolutely nothing wrong with gating to a lower pressure than you're tuned for.

OP, have you inspected all of your mounts?

azzazel_9

So being tuned for a high boost like that with fuel and what not then running lower boost but still getting the same large amount of afr wont effect how the motor runs? I would have thought unless it is retuned for the lower psi it would be dumping alot more fuel than needed for the lower boost and cause it to run rich or something. My logic is wrong sorry for the mis informed idea.

jbpnoman

How boost works in relation to the ECU and fuel maps is too complicated for this section (and doesn't belong here, anyway), but to be tuned for 35 PSI, it has to be tuned for 35, 34, 33, 32, 31...you get the point. Boost doesn't just suddenly go from -14 to 35 - it has to go through everything in between, and a proper tune accounts for all of that.

azzazel_9

Makes since thanks for the explanation.



This is just another reason i don't buy other peoples boosted or swapped setups because you never really know what its been through or if it was done correctly. Hope the op gets it figured out though.