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4.9 performance thoughts


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after lots of thought on how to get more power out of my seville (93 w/ 4.9) I have pretty much decided to go with forced induction (more than likley turbocharged for the ease of mounting, I cannot see an easy way to supercharge without relocating the alternator etc)

I was able to pick up a 92 sdv for $500 that needs body and interior work, but seems mechanically solid (now nicknamed the guinea pig). Making the custom manifolds does not bother me, and I have found a place that will rebuild the tranny and guarntee it for the power levels I am trying to achieve, the real concern I have is about the computer tuning. Has anyone tried this, and anyone have suggestion on where to look for someone to do totally custom chip programming (or is this another thing I need to learn myself B) )

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Custom programming like that I think you will need to find somone local to you who can tune the car on the dyno and update the calibration (programming) as needed.


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you sound very brave and ready to work on cars, but I would go with the northstar, having both of the engines myself, the 4.9 really is a dog in comparison. Put some good mufflers and intake on a 4.6L and your talking 300-325HP easy. Much more than a turboed 4.9L will make, and a lot less work. Plus, the 4.9 liters transmission is limited to 5000rpm, a big disadvantage if you are talking about super or turbocharging the 4.9L. The northstars trans is a much better unit, much more intelligent in its shifting and algorithms and such.


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I had a rental Deville with the 4.9 and drove it about 500 miles. It had amazing torque. More than my high reving Northstar. I think the 4.9 is a good candidate for a hot rod engine. Not as expensive as the Northstar.


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My 4.9 is quite a feisty and spunky engine. Like a greyhound, which is the nickname of my car.

If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans.

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this is on the mild side of undertakings I have had. Just to throw out some thoughts more than anything for the purpose of reaction and clarification, here is what all is going on in my head.

Although I do like the northstar, I really like the low end torque of the 4.9, and the seville has about 55k miles on it and is in near showroom condition, so there is plenty of life left in it, as far as I can see, finding a N* car in this condition would easily set me back another $13+k (mine is paid for :) )

The transmission is not a big deal in my mind as I have already found a shop to rebuild and guarntee it up to 500ft/lbs, as far as the shifting algorythims, when I am driving in a more spirited fashion, I shift manually anyway.

One very big drawback to the N* cars in my mind is the traction control...it was built around a factory spec power curve and output, and as I understand, you can still overheat the brakes if you are slamming it too hard for too long, the idea of having over monsterous torque under my right foot is great provided the tires can act as an outlet, and not the brakes and all related components. Something about burning up the tires sounds much more apealing than dealing with brake fade

From the power side, based on what I am figuring (both from raw calculations, and experience from custom building 6 other cars) I should be able to pull somewhere near 295hp and 400ft/lbs with a somewhat flatter power curve than stock.

I am taking the guniea pig to get dynoed next week so we have a reference of the starting point of this project as far as actual fwhp numbers....

sidenote: there is something about getting close to 400ft/lbs in a front wheel drive that just screems to prepare for massive torque steer, its up there with the thoughts of the days when detroit muscle equated to lifting the front wheels off the ground and bending frames.

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Take a look at this website:


With 20 psi. of boost, the 4.9 should be faster than the Northstar.

To get around the fueling calibration, you might want to investigate a completely programable fuel injection system called Megasquirt. I believe you can hook up the Megasquirt system right to the existing hardware (02 sensors, fuel injectors, etc). Or you might be able to use the Megasquirt system to run another injector that would add the extra gas that the turbo setup would need.

Here's a website that gives information on this system.


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I put a K&N air filter and some hi-perf wires/plugs/cap/rotor and my old 4.9 does pretty well for having 140,000 on it. The only thing that drives me nuts is that low end thump it has. I guess from what I understand....that was normal in some of the 4.9's??? makes me nervous evertime I listen. I keep thinking I am going to throw a rod. Good luck with the HP gain.

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