KA-T loses power when boost hits

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ericmcgarrh
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KA-T loses power when boost hits

Post by ericmcgarrh »

just want to get some opinions on a problem im having with my freshly installed ka-t.
specs
fully rebuilt motor with stock internals/arp hardware
enthalpy tune
gt2860rs/550cc/z32 maf/walbro 255lph
ngk bkr7e gapped to .028
full exhaust
fmic
tial qr bov(recirced)
aem wideband
aem truboost

it started up first try and idled on first start, go me. idle is kinda high, around 1400. idle afr is between 16-17, lean. wot afr goes as low as 10.2, rich. revs parked in the driveway register boost (up to 8 psi) and the bov opens when the throttle body closes, functioning properly. take it on its first drive and the second it hits boost it falls on its face like it loses power, like less than stock ka power and will barely pull its own ass. anyone ever experience this? if so what was your problem?
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airman
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Re: KA-T loses power when boost hits

Post by airman »

The 10.2 WOT is likely your issue - the excess fuel is probably blowing our your spark. Boost AFRs should be in the mid-low 11s for unleaded gasoline.
R.I.P. 1990 Red Hatch - DOHC 5 speed // CP 9:1 - Eagle Rods - Clevite - ARP // Holset HX35 - 20psi daily - MSPNP2
8-bit wrote:You could spend your life building a ladder to the moon, or work for 5 years to pay for a trip.
2hunglow1standhi
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Re: KA-T loses power when boost hits

Post by 2hunglow1standhi »

Go tru the normal checks. Timing, boost leaks, what did Enthalpy say?

Strange your able to build 8 psi revving "parked"?

And are you Blow through? Or suck through?
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ericmcgarrh
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Re: KA-T loses power when boost hits

Post by ericmcgarrh »

well when parked i can rev it and the boost gauge goes up to 8 psi and the gauge gets its reading directly from the intake manifold. i am draw through
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airman
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Re: KA-T loses power when boost hits

Post by airman »

You shouldn't be boosting at idle. Something really sounds like you are running much too rich.
R.I.P. 1990 Red Hatch - DOHC 5 speed // CP 9:1 - Eagle Rods - Clevite - ARP // Holset HX35 - 20psi daily - MSPNP2
8-bit wrote:You could spend your life building a ladder to the moon, or work for 5 years to pay for a trip.
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BigLoukaT
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Re: KA-T loses power when boost hits

Post by BigLoukaT »

Timing way retarded would probably cause this too.

Have you verified base timing is set correctly? Definitely should not be boosting under no load
1990 S13
Boosted single slammer
MS DIYPNP
npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.
ericmcgarrh
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Re: KA-T loses power when boost hits

Post by ericmcgarrh »

well im really not sure how it made boost with no load but it definitely did because the gauge registered it and the bov released the air when i let off. it no longer builds boost with no load. not sure how that fixed itself. i did do a boost leak test and found a few leaks and fixed them. now that they are fixed the car idles at 14.6 afr most of the time but sometimes its still around 16-17 afr . and the vacuum has increased up to 19-21. cruising the afr is usually between 13-15 afr and under throttle its still between 10.2-11.6 afr. i dont understand this at all. sometimes the car will pull great, usually after first starting it and letting it warm up. its like the first time it goes into boost itll pull through the gears and then after just cruising, try to get on it again and the boost hits and the motor just bogs. but when its bogging the boost is reading steady and in line with how much throttle im giving, the car just isnt going anywhere. another weird issue is when i am having this problem i can pull over and shut the car off and let it sit for just a few minutes and then start it back up and take off again and sometimes it will pull again like the problem is not there at all. but then others its like it didnt affect it at all. im losing my mind here
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supakat
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Re: KA-T loses power when boost hits

Post by supakat »

Sounds like you may be getting knock and ecu goes to knock map.
12.96 @ 116.36 - 2.1 60ft - 11/2011
13.1 @ 114 - 2.3 60ft - 8/2012
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ericmcgarrh
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Re: KA-T loses power when boost hits

Post by ericmcgarrh »

supakat ive been hoping you would see this post. i have seen your knowledge all over the forum! if the sensor did detect knock and it went into the knock map, wouldnt it store a code for the knock sensor? i have disconnected the knock sensor to see if it drove differently without it and it didnt help or hurt it. but when i disconnected it it did store code 34. but that is the only time it has stored that code. the knock sensor is a brand new oem part.
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supakat
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Re: KA-T loses power when boost hits

Post by supakat »

Thank you for the comment. We have quite a few members on here who are knowledgeable as well. It is better to have more heads than one on an issue hence why this forum is pretty helpful.

Back to the issue, It should throw a CEL if detected but we do not know if Martin turned knock feedback off. I had it off when I was chipped. It could be a temp issue possibly. Can you install an aftermarket temp gauge? Could be when it is too hot, dumps fuel and retards timing. I am unsure what Nistune/TunerPRO may call it but in TS we call it MAT correction. AEM calls it fuel/ignition trims based on IAT. Maybe you can gut your t stat and see if it happens. I just did some tuning at 25 psi and after 3 pulls coolant is 189* and MAT is around 100* but drops down quickly.
12.96 @ 116.36 - 2.1 60ft - 11/2011
13.1 @ 114 - 2.3 60ft - 8/2012
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