kikiturbo

Had a couple of sleepless nights with a car I am building for a buddy, and finally came to a solution... Found online that there are people with similar problems so wanted to share..

Engine spec: Stock block, head taken off, ports just cleaned off any casting marks, valve bowl core shift fixed as well as we could without adding material.

S2 cams, kiggley springs, courtesy of english Racing.. ASNU 1000 CC injectors
HKS 7460 kai, on stock ported manifold, exhaust turbine housing also ported, ceramic coated. Larger IC (cheap chinese made item), 2.5 inch custom IC piping with absolute minimum of bends (routing trough the drivers side wing)

ETS intake


The problem... Really rough idle, can't idle on it's own at all when warm, pig ritch @idle (10.5 to 11.5), changing the fueling troughout the rpm range when stationary.

Due to this we couldn't adjust the cc and latency of ASNU injectors (I like to adjust it roughy with the car sationary, just to be in the ballpark) because AFR were all over the place.

Switched back to stock injectors.. again same symptoms.. pig ritch up to 2000 rpm, ok afterwards.
Funnily enough, car drove fine, even if it was running just the base map, no hiccups, nothing.. just really bad idle.

Thought I had a really bad cam overlap problem, adjusted MIVEC to 0 to -1.2 deg cam timing at idle and low rpm.. no difference. Removed EGR.. same thing..

then I saw threads about HKS sopooling on idle, and said, ok let's check if the MAF was working overtime on idle.
At the same time Petteri suggested that I remove the ETS intake, which is metal, because the metal pipe might introduce some harmonics into the system and mess up the MAF..

I unplugged the MAF.. and hey, presto... smooth idle.. Then I removed the ETS intake and went for the OE rubber intake.. with KN filter on still, and again, correct AFR and ok idle...

Here are some vids.. with AFR.. 

1. Everything connected, ETS metal intake on the turbo… ritch AFR and you can hear the engine missing on idle… actually this is relatively good behavior as when it is warm it will not run at all on idle and will hiccup until 2000 rpm.. turn up the volume you can hear it..
http://vidmg.photobucket.com/albums/...929_103326.mp4


2. Unpluged the MAF… as you can see the engine purrs like a kitten.. 
http://vidmg.photobucket.com/albums/...929_103237.mp4


3. OEM rubber pipe back on the car..  MAF connected…
http://vidmg.photobucket.com/albums/...929_104621.mp4


please note that this is all still untuned, running in open loop…

94AWDcoupe

iTrader: (125)

this is a bb turbo problem. my bb fp red messes with maf signal around idle. there is no way to tune it out with a maf setup. speed density is the way forward.

kikiturbo

what kind of intake pipe are you running..?

meckert

iTrader: (11)

From what you wrote-- sounds like you simply need to support the maf and make sure the intake is supported and held steady in place. Its not a function of the turbo. I have the HKS turbo and have never had or read of idle issues with it--the s2's you have, have a great reputation-
As for my recommendation on the intake thats been all over this forum, at least several years ago-- some folks had Harley's pull up next to them at a light and it caused idle issues.. So try and build a bracket to support and isolate the intake tube-- Its simple, cheap and should do the trick. GL

kikiturbo

there was no difference in support between ETS and OEM intake.. the only difference is that one is mainly metal and other rubber..

kamote2000

iTrader: (7)

Good day sir this looks like a good solution im on the hks 7460r turbo as well. And since getting that turbo i have had idling problems all around, idle dips to 500 rpms at stoplights, idle hangs, already made adjustments with the tune idle somewhat went better but still there. And yes im on hks hard intake tube mushroom filter. But with stock turbo, hks hard tube and mushroom filter never had idling issues. Do you think the samco silicone intake tube would also be able to fix my idling issues as well. But im gonna give the stock intake tube a try. Thanks for sharing.

Terror Rising

iTrader: (26)

That's a huge difference. A stock MAF is supported by the intake box and the rubber pipe is the flex joint. Thus the MAF moves very minimally. Now take the stock intake box off and replace it with a cone filter. The MAF is no longer supported but the rubber intake pipe still doesn't transmit enough vibration to affect the MAF readings (think of it as a damper). Now add a hard pipe into the equation. The MAF is not supported, the hard pipe readily transmits vibration, and your MAF readings get screwed up.

TommiM

iTrader: (19)

I remember a while back, a local evo owner tested a few different intake setups and found maf issues causing erratic idle and what not with the hard tube intake pipes. He found the ones that were more maf friendly were the softer material ones like oem or the samco ones.