I have a 97 Dodge Dakota ,I installed dual exhaust and was wanting to
know if anyone knew of some simple power mods that can be done to give
my weak 3.9 , a little more 'power ? I saw a spacer that goes between
the air intake and the intake manifold in Summit catalog that "claims" a
power increase, has anyone in here ever installed one of those and
recieved the "claimed" power increase ? Would a hotter ignition coil
help maybe ? Thanks !
That should be about the same thing as a high rise manifold that we used to
use back in the 70's to increase power and fuel economy. Back then we were
very surprised that when we added spacers under the carb, between the carb
and the intake, it actually increase fuel economy and performance. If there
is a way to open up the exhaust as well, such as headers, that will improve
it more than anything else you could do. But I don't know how legal it is to
add headers anymore since the introduction of the catalytic converter. I saw
an article in pop hot rod in the mid 80's where they took Ford catalytic
converters and put them on Chevy vehicles to increase performance, it seems
that at least back then the Ford converters were more open and didn't choke
down the exhaust as much as the other vehicle makers. They may all use the
same converters now though, I don't know, I have not worked on an engine in
While it should be, it actually isn't. You are talking about too very
different animals here.
Yes they did and for many reasons. First, they kept the carb cooler which
allowed for a denser fuel charge (performance), second, they helped in the
mixing of the air and fuel prior to entering the cylinder (economy) and
third, in some cases they increased the air flow velocity which helped to
cram more air and fuel into the cylinders (performance). In a modern
computer controlled multi-port fuel injected engine, the first two reasons
are eliminated and all that is left is the last one and even there, unless
the design was inefficient (much more common with the factory manifolds of
the 70's), there is little chance of any ram effect either so the only real
mileage improvement comes from the weight loss of your wallet.
Once again, this is incorrect. Todays engines are specifically set up to
run the way they were built. Opening up the exhaust even in the past helped
the most at higher engine RPM's. Todays engines are configured to run with
an expected amount of back pressure and the valve timing is set up with that
in mind. IF you open up the exhaust, you will be spitting some of your air
fuel charge into the exhaust and the O2 sensor will see that as a run rich
condition and lean out the mixture. This will result in less power which
will also reduce mileage and create a high ping rate as well.
I am unaware of any law against adding headers as long as they are
compatable with the emmissions standards of the vehicle.
With the push for better economy, I would say that for the most part, the
factory converters for standard passenger vehicles are all just about the
same for flow characteristics.
If at first you don't succeed, you're not cut out for skydiving >
here are a few things I found while looking for info on my dodge stealth RT.
Seems to be applicapble to most vehicles.
There is really not much that you can do to that engine to increase its
power. I'm not sure if there is a power programmer available for that
engine but if there is, that is just about the only simple (but not cheap)
method that I am aware of for that engine. As for those spacers, with
today's computer controlled fuel injected engines, unless there is a flaw in
the design of the intake manifold to begin with, they have little to no
effect. Now if you want real power, you could always super or turbo charge
it and there may be a supercharger kit available for that engine.
If at first you don't succeed, you're not cut out for skydiving
"Joe Cool" < email@example.com> wrote in message
I have built and driven many high performance vehicles in my life and the
one thing I can say is that it is never simple nor inexpensive. Today, it is
even more complex than 30 years ago. I can also state that the most
effective mod is always cubic inches. High Tech is expensive and the return
is less effective than more inches. It is also safe to say that any money
invested in performance must be considered lost financially. You will never
realize the investment in increased sales price when changing vehicles. So,
my advice is to find a wrecked late model with a 5.9, buy it complete with
gearbox, wiring harness and computer and swap out the 3.9. It will be
worthwhile both in performance and economy, as well as affordable fun.
The air spacer doesn't work. I've never seen a
single dyno sheet that proves it. There's no fuel in
that area, so all it does is change the air flow.
In the old days - carb days - getting more power
from a stock engine was pretty simple. The factory has
a very conservative tune, so you just made it more
"aggressive". Add timing, add fuel. That has to be
done by reprogramming the computer. Check with Jet and
Moving the air in and out better is usually worth
something. The factory exhaust is pretty good. After
market systems will improve power at the top end. But
you don't get a lot of nag for the buck there.
A cold air induction is actually worth some
power. The factory intake is kinda restrictive. A
drop in K&N air filter won't help at all, though.
Another tried and true method is changing the
rocker arms to a bigger ratio. Increasing the rocker
arm ratio is like adding a slightly bigger cam.
All magnum engines use the same design rocker
arm. The 3.9, 5.2, and 5.9 use exactly the same parts.
But the V-10 uses a longer ratio. Swap in the V-10
parts and gain some noticeable power. I have a set for
my 5.9 sitting in the garage waiting for me to install
Don't forget the non-engine improvements - lower
gear ratio, lower weight, better aerodynamics, low drag
Funny how back in the 70's I had a 71 ford Torino GT(351 cleveland, factory
holley 4 barrel with vacuum secondaries) and stock off the lot it got 28
miles to the gallon on the highway and in those days I rarely dropped below
90. My Dad told me I was lying until he and I drove it to Miami one week. He
hasn't stopped talking about that car since. After the octane dropped below
100 it wasn't drivable so I sold it.
What causes that is the NO restriction. All engines are heat engines and the
more heat you can generate from a given fuel charge, the greater the air
charge expansion and more power, but when temperatures exceed 3500 degrees F
in the chamber, the nitrogen in the air charge will combine with the free
oxygen molecules and create NO in the exhaust gases. By reducing that peak
temperature below 3500, it drastically reduces the NO. Hence we have EGR and
lower compression ratios. This introduces thermal inefficiency and we have
poor economy. It's a trade off.
when they start using ethanol more will that raise the octane, slow the
burn? So they could raise the compression ratio and get the economy up?
Seems it would be better to get the economy up with supply going down.
That's a loaded question. Yes, alcohol allows a higher compression ratio
without detonation risk, but the 3500 degree NO problem is still there.
Ethanol has 85% of the latent energy of gasoline, so your mileage will be
15% less on pure ethanol right up front. With methanol, you will lose 30%
and natural gas 25%. Diesel, on the other hand has 25% more latent heat by
volume and you with realize 25% increase in mileage. Interestingly, all
these hydrocarbon fuels have the same energy by weight. There is no free
lunch. As long as the NO emission rule is enforced, thermal efficiency will
be compromized. Great strides have been made with diesels however. This has
been realized by the multiple injection events per cylinder cycle. By doing
this, peak pressure and temperature has been reduced, which reduced the
typical diesel clatter (detonation), allows lighter weight crank and block
assemblies and higher engine speeds.(broader power band). Of course this has
had the effect of also reducing thermal efficiency somewhat from .39 lbs per
HP hour (BSFC) to about .42 lbs per HP hour, but as long as we buy fuel by
volume and not weight, diesel is the hot setup.
I have the 2" spacer in my 318 1995 4WD SLT and I also put in an MSD coil,
dual exhaust, Mopar HP computer and K&N filter. The biggest gain was in fuel
economy that went from 13mpg average to 17mpg. Highway milage is almost
18mpg, but not quite.......:-). Torque increased quite a bit too with it not
shifting much on small-medium grades when towing. I just went over 172,000
miles and it still runs great with no oil usage. These modifications have
been installed since it was at about 50,000 miles and the savings in fuel
alone has paid for them several times.
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