| Re: [GMCnet] MPG and TBI questions [message #111608] |
Mon, 10 January 2011 20:32 |
Gary Casey
Messages: 448
Registered: September 2009
Karma:
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Senior Member |
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I'm mostly with Rob on this one - in the neutral corner. But.... I don't see
how changing to a TBI system could get 20% better mileage. The carb will suffer
during warmup as it is very difficult to get the choke adjust perfectly. But
cold starts consume a very small portion of the total fuel in most of our
coaches. Another problem is WOT - the Q-jet has pretty poor air/fuel
distribution on the secondaries. But again, I'll bet this represents a small
portion of the total operating time. Most of the fuel is burn, I'll bet, during
part throttle cruise conditions and Q-jet running the same air/fuel ratio will
be just as good as a TBI system. I just can't agree with a 20% improvement with
TBI. Will it run more consistently good? Sure, and that is what we have come
to expect with the EFI cars we all drive. I would like to have EFI on my coach,
but after 30 or so years developing EFI systems and having one in a box in my
garage, I'm still running a Q-jet. Jim B. makes some valid points.
Gary Casey
Dave,
One thing:
Insert Jim B's standard rant about EFI vs. carbs below. ;-)
http://www.gmccoop.com/new_page_15.htm
I am playing Switzerland in this argument, neutral. The Blue Streak here in
Australia has a Holley Commander 950 EFI and I can tell you in comparison to
Double Trouble it goes like a scalded cat! However, as I noted in a recent
e-mail I've bought a rebuilt QuadraJet off eBay to carry with me on trips to
the Outback!
When the Caddy (LPG) engine is ready to be installed I'll probably take the
Edelbrock and Holley off and bring it to the USA and install it on Double
Trouble.
I am planning on setting up the Caddy to run on LPG only, however, Mark
Bennett has suggested I consider that carefully as he thinks it would be
prudent to leave the petrol tanks in there (at least one) just in case the
LPG system has problems.
Regards,
Rob M.
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