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Boost issue in 5th gear 100kph

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Boost issue in 5th gear 100kph

Postby tonkamu » Fri Sep 22, 2017 9:30 am

Not sure if this is an engine or drive train question. I'm running 15-17 PSI, 2'5" exhaust and fuel increased my car is 2.8.

On the motorway I see constant 7-10psi on flat road cruising along in 5h gear doing around 90-100kph, if I slightly accelerate it will boost to 15-17 psi until I ease off to keep a regular speed & boost hovers around 10psi. Its like its always loaded in 5th gear at highspeeds, I've had this problem with 31 inch wheels aswell. Could someone shed some light on this?
tonkamu
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Vehicle: 2.8 Mu 1991 All Black. MODS - Rear Lifted 2.5" Lovells Leafs / Rear Lokka / 33" Achilles / 9500 RUNVA w plug n kills switch inside cab / EGT, Voltage, Turbo timer, Boost gauge / 20 PSI VF10 Turbo with VF10 exhaust housing 2.5" downpipe with merged 2" wastegate pipe to full 2.5" straight pipe / GFB Boost Tap / Maxed fuel with grinded down cable stop / Adjusted Boost Compensator / 3.1 Oil Cooler / Intercooled / 3" Custom intake to sealed K&N airbox & filter to Snorkel / Catch Can / Xtreme Outback HD clutch / RockfordFosgate 300rms AMP w 2X Rockford Power 6x9's BT HDeck / all EGR, QWS, AC pump deleted.

Re: Boost issue in 5th gear 100kph

Postby geeves » Fri Sep 22, 2017 10:55 am

Thats called normal
Boost is developed by exhaust flow which is affected by fuel use engine speed etc. Cruising at 100kph you have a fairly high engine speed but low fuel use so there is not enough exhaust flow to give full boost not that you need it in that situation. put the foot down and for the same engine speed you have more fuel so more exhaust flow so more boost
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Boost issue in 5th gear 100kph

Postby tonkamu » Fri Sep 22, 2017 1:40 pm

Oh ok cool, so cursing with 10psi for long period of time isn't wearing anything out?
tonkamu
Isuzu Junior
 
Posts: 117
Joined: Sun Jan 01, 2017 7:23 am
Age: 36
Country: NZ
City: Auckland
Vehicle: 2.8 Mu 1991 All Black. MODS - Rear Lifted 2.5" Lovells Leafs / Rear Lokka / 33" Achilles / 9500 RUNVA w plug n kills switch inside cab / EGT, Voltage, Turbo timer, Boost gauge / 20 PSI VF10 Turbo with VF10 exhaust housing 2.5" downpipe with merged 2" wastegate pipe to full 2.5" straight pipe / GFB Boost Tap / Maxed fuel with grinded down cable stop / Adjusted Boost Compensator / 3.1 Oil Cooler / Intercooled / 3" Custom intake to sealed K&N airbox & filter to Snorkel / Catch Can / Xtreme Outback HD clutch / RockfordFosgate 300rms AMP w 2X Rockford Power 6x9's BT HDeck / all EGR, QWS, AC pump deleted.

Re: Boost issue in 5th gear 100kph

Postby geeves » Fri Sep 22, 2017 4:40 pm

no racing with it at 17 is though
Sanding your knuckles before starting work can help. That way you cant skin them
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geeves
Site Admin
 
Posts: 8178
Joined: Sun May 10, 2009 1:36 pm
Location: wellington
Age: 55
Country: NZ
City: Wellington
Vehicle: 94 bighorn
96 wizard


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