Northstar 4.0 mods?
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Northstar Engines and System Technical Discussion Discussion, Northstar 4.0 mods? in Cadillac Engine Technical Discussion; Just got a 98' Aurora and have already decided that once I get my loan paid in full I will ...
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    Northstar 4.0 mods?

    Just got a 98' Aurora and have already decided that once I get my loan paid in full I will begin to modify my car a little. The car has Northstars smaller 4.0 liter V8 engine, thats why i'm asking in here. Can anyone tell me what mods are available to Aurora's? I would lke to do at the very least exhaust and intake to wake things up a little. I am also considering a possiblilty for a new PCM. I don't even know if one is available, but if there is one that I can get to override the speed limiter and other computer controlled things that'd be great. Well, thanks for any information anyone can provide me with.


    -Kevin

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    Re: Northstar 4.0 mods?

    Pretty much the same stuff that's available for the 4.6L V8. Which is to say, not a lot. A freer exhaust will help, and there are some easy airbox mods you can do to help it breath a little better. RSM makes a bored throttle-body for the classic.

    My suggestion, get a Corsa, a K&N, mod the airbox, and enjoy the car...

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    Re: Northstar 4.0 mods?

    Quote Originally Posted by Rambo
    Just got a 98' Aurora and have already decided that once I get my loan paid in full I will begin to modify my car a little. The car has Northstars smaller 4.0 liter V8 engine, thats why i'm asking in here. Can anyone tell me what mods are available to Aurora's? I would lke to do at the very least exhaust and intake to wake things up a little. I am also considering a possiblilty for a new PCM. I don't even know if one is available, but if there is one that I can get to override the speed limiter and other computer controlled things that'd be great. Well, thanks for any information anyone can provide me with.


    -Kevin
    Uh...RAMBO would not be caught dead driving a 4.0 Aurora.....unless it had NOS or a supercharger.....LOL....just kidding. Really.

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    Re: Northstar 4.0 mods?

    Quote Originally Posted by bbob
    Uh...RAMBO would not be caught dead driving a 4.0 Aurora.....unless it had NOS or a supercharger.....LOL....just kidding. Really.
    Yeah he wouldn't be caught dead with a 4.0....only cause he couldn't handle it. LOL

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    Re: Northstar 4.0 mods?

    I thought it was because he's too ugly. An attractive car like the Aurora needs an attractive person to pilot it.

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    Re: Northstar 4.0 mods?

    Quote Originally Posted by Aurora40
    I thought it was because he's too ugly. An attractive car like the Aurora needs an attractive person to pilot it.
    Well yeah, that too, obviously... LOL

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    Re: Northstar 4.0 mods?

    Quote Originally Posted by Aurora40
    Pretty much the same stuff that's available for the 4.6L V8. Which is to say, not a lot. A freer exhaust will help, and there are some easy airbox mods you can do to help it breath a little better. RSM makes a bored throttle-body for the classic.

    My suggestion, get a Corsa, a K&N, mod the airbox, and enjoy the car...

    First: Is the exhuast on a 4.0 the same as on a 4.6? As in Cat, into resonator, into dual mufflers? If so, would I be wise as to replace the cat with a hi-flow unit, ditch the resonator, and get some free flowing mufflers such as the suggested corsa? Does Corsa make a direct bolt on muffler system for Aurora's?

    Second: Does K&N make a FIPK cold-air induction system or do you just recommend I do the free air box mod along with a K&N filter?

    Third: Will a bored-out throttle body even help at all?

    Fourth: Do I have any other options?

    Fifth: Why is everyone making fun of Rambo?

    Sixth: I need to make a lot more money!

    Thanks!

    -Kevin

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    Re: Northstar 4.0 mods?

    I'm not sure if the exhaust is exactly the same, but it is similar. Corsa does not make a direct replacement, but the Seville system can be modded to fit by a local shop. It is a cat-back system, and includes a resonator. You can see right through all of it (mufflers included), so I don't see how replacing the resonator with straight pipe would gain very much. It is almost a straight pipe already except for a small gap for sound waves to enter.

    I don't think K&N makes a FIPK. I just meant the panel filter and the free airbox mod. You could try a cone, but I wouldn't unless you built some sort of shield/chamber to keep it away from engine heated air.

    The TB, some say yes, some say no. A few people with the Aurora dynoed it for about a 9hp gain at the wheels. Even if the extra size isn't needed, having it ported makes it all much smoother for flow. Otherwise, on the classic, the TB is about 75mm, the spacer behind it is 78mm and the intake manifold entrance is 80mm. So even though it gets bigger, it does not do so in a smooth fashion, which can affect the flow. But you have to decide if you think it will help.

    I'm not aware of too many other options. There has been talk of a 4.6 supercharger for years, and domesticperformance.com claims to be taking orders for an Aurora supercharger.

    Also, I personally don't see how high-flow cats can actually flow more unless they do a worse job catalyzing stuff. Most people who have replaced theirs have had the MIL light come on. I wouldn't swap mine out just for the possible gain. But again, it's up to you.

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    Re: Northstar 4.0 mods?

    One of the guys with a Northstar tried the larger throttle body and it did nothing for performance at the dragstrip even with exhaust and inlet mods...

    Based on the sizing of the production throttle body it will support even more power so I can't understand how a bigger one would show more power.

    How on earth someone dyno'd a 4.0 and got more power with a larger throttle body is beyond my understanding. The production throttle body is plenty big enough for even a 4.6 much less a 4.0....must be the same shop dynoing the car that sold him the throttle body....LOL....dyno results, especially chassis dyno results, can show many erroneous things depending on what the operator is wanting to see....especially if the runs are on different days....

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    Re: Northstar 4.0 mods?

    first off, you talk of removing the speed limiter. there are 2 versions of aurora's. 1 has a limiter of 112 and 3.48 gears. the other has a limiter of 139 (some places claim 135, but ive seen 139 before i ran out of road) and 3.71 gears. open your drivers side door, check what the oem tires were. if it says they were V rated, you have the higher limiter and better gearing. (it'll say 235/60/16 V instead of 235/60/16 S) or check your spare tire cover for option QQX which stands for the autobahn package (what its called).

    for exhaust id get a highflow cat. you can get a carsounds for $50. you'll need a $10 o2 simulator also so your MIL light doesn't go off. i changed out all of my exhaust, then the cat and noticed a improvement, a pretty big one i think. then go 2.5" all the way back, get a strait through racing muffler or glasspack for a resonator. i don't have a resonator and i plan on getting one because of the highway drone i get. then it splits, and get 2 more strait through mufflers. corsa exhaust is awesome, but very very expensive (1,000 plus install, maybe another 250). expect to pay in the area of 600 for a complete exhaust from cat to tips and install. check out caddyinfo.com for instructions on how to mod your airbox.

    i personally wouldn't spend the money on the bigger TB, maybe if i had a 4.6, but the 4.0 already has the same 74-75mm TB as the bigger 4.6, and a 4.0 doesn't breath as hard. ive heard of 4.6's seeing little to no improvement, its NOT a cheap mod either. domesticperformance.com should be able to hook you up with a reprogrammed pcm, id do that before a TB

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    Re: Northstar 4.0 mods?

    Just a few notes...

    I'm not endorsing anyone get the bigger TB, but it isn't really that expensive. I believe it's like $200 from RSM. I guess I don't consider that an expensive mod.

    Also, Bbob, you mentioned that the 75mm is plenty big for the 4.6, but the RWD 4.6 actually went to an 80mm TB, and it only move the fuel cutoff 50rpm up the scale. Also, even if the larger size isn't warranted, it should flow better than the mismatched size that's there previously. It is 75-78-80mm. I would bet if it were all 75mm and matched up that it would flow better than the expasion does (especially a jagged expansion like that).

    And you said someone went to the track to test it and noticed no improvement. While a chasis dyno is not a perfect tool, it is quite a bit more controllable and repeatable than going to the 1/4 mile track... And the tests I'd seen were on the same day, I doubt the same is true of the 1/4 mile guy (as that'd be interesting swapping your TB out at the track). And none were by shops in any way affiliated with the sale of the product. They were on purchasers cars at local dynos, not numbers supplied by the TB maker.

    I'm not saying the TB is worth the money or that it does anything, what I'm saying is I think it shouldn't just be dismissed out of hand like that.

    Also, that's what I meant about the "high-flow" cats. Really, they aren't high-flow, they are just bad at catalyzing. To me, high-flow implies they do the same job but can flow a lot more. In fact, they do a poor job which is why they flow more, and they set off your MIL because of it. It's sort of like calling a piece of straight-pipe a "high flow cat"... If you are gonna do that, why not just gut your cat for free and retain the stock appearance and your money? Just an opinion.

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    Re: Northstar 4.0 mods?

    I wasn't dismissing them out of hand. I have tested larger ones on engine dyno tests and they did nothing for power on a production Northstar engine. If other mods were made to increase air flow then a larger throttle body might be adviseable but not on the production engine as is....


    Chassis dynos are good...but only as good as the operator. They can be made to read whatever you or the operator wants.... Besides, the goal is to go faster on the dragstrip, not spin the chassis dyno. Back to back passes at the strip in a short termaround time are a pretty good comparison of the two throttle bodies as it was done. My point was that a reasonable test was done with the larger throttle body and the results in the real world matched the engine dyno results. Sometimes a dragstrip run is actually more repeatitive than a chassis dyno...if the engine heats up or the underhood temps go up the readings can change significantly. Hard to keep a car cool on the chassis dyno for many runs.

    This is getting to be a tough crowd....LOL.....You are comparing apples to oranges in a way with the transverse (FWD) and longitundinal (RWD) Northstar throttle bodies. Definitely a valid question though. First, the RWD engine makes 320 HP as is. so it can use a slightly bigger throttle body...and it is the first version of the RWD Northstar engine family....more to come...so why size the throttle body for what we have today....catch my drift??? Second, the throttle body on the RWD engine is a drive by wire electronic throttle body that has to be incorporated into the electrical architecture of the vehicle....so one might size it larger than currently needed since it will be more difficult to change in the future and very expensive if we had to change the size of the throttle body...so , since it was new to the engine for 04 there was a little forward planning going on there.

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    Re: Northstar 4.0 mods?

    Quote Originally Posted by Dubya
    first off, you talk of removing the speed limiter. there are 2 versions of aurora's. 1 has a limiter of 112 and 3.48 gears. the other has a limiter of 139 (some places claim 135, but ive seen 139 before i ran out of road) and 3.71 gears. open your drivers side door, check what the oem tires were. if it says they were V rated, you have the higher limiter and better gearing. (it'll say 235/60/16 V instead of 235/60/16 S) or check your spare tire cover for option QQX which stands for the autobahn package (what its called).

    domesticperformance.com should be able to hook you up with a reprogrammed pcm, id do that before a TB
    Do you think it would be at all possible to get a Autobahn version PCM? Is this even possible? If so, how much would one run, where would I get it, and how hard would it be to install?


    Thank you!

    -Kevin

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    Re: Northstar 4.0 mods?

    1st, a autobahn pcm would also make the car think you'd have 3.71 gears, and mess all kinds of stuff up

    i remember this TB vs highflow cat discussion on edmunds, lol, you are scewing the numbers some there. they're $250, but you need the matched mount plate, $100 more. so $350, plus the cost of a new TB, unless you can have your car down for 1-2 weeks.

    highflow cats arn't just cheap cats, there much more expensive to make. we went over this before. there made of better materials. because these better materials catilyze (SP?) better, they are allowed to use less material to get the same effect, which means shorter bricks, more flow. they have very strict rules to apply by, and are CARB legal, no way they can be CARB if there just "bad oem cats". they also have more expensive casings in which all the rough edges and little ridges are gone. this is also a $50 mod vs a $350 mod.

    not only this, both the TB and the cat can sorta plug up, droping flow. you can clean the TB, i did and noticed a good improvement in power and response. these dyno's showing all this power increase is a dirty oem vs a clean bored out one. the 5-8hp improvement garnes got would have been less, clean vs clean. you can't clean a cat, so a new one is needed

    and serioulsy seriously sersiously saying a VVT RWD 4.6 northstar having a 80mm tb means that a fwd 4.0 northstar would benifit is like saying we should also put a 80mm TB on the 3.5 dohc, why stop there, even the 2.2 cavilier motor. not only is the 4.6 bigger so it breathes harder, it has VVT which contributes to needing more air. i don't understand why you and garnes keep bringing up this point, its not releavant at all. that engine even revs higher than the classic aurora (only years tb could even apply)

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    Re: Northstar 4.0 mods?

    Wow... Way to make an argument where there wasn't one... At what point did I compare the 80mm 4.6 TB to the 75mm 4.0 TB? I believe I addressed a point where Bbob said the 4.6 doesn't even need a bigger TB. You're right, RSM has it for $250 not $200. I think it used to be $200.

    I also don't believe I said the TB was a better buy than the cat. Nor did I say the high-flow cat wouldn't free power. These are more arguments you must have dreamed up. What I said is that they don't do as good a job catalyzing. If they do as good or better than an OEM cat, why is it they set your MIL light? Why would you need a fake O2 sensor? I'm also a bit surprised that they can use better materials, better machining, and still sell one for $50. What are these better materials, anyway? The catalyzing agents in an OEM cat are very expensive precious metals. So what's the modern miracle catalyzing agent that is in a Carsounds cat? If you are going by the claims on websites like Random Technologies, they compare their "modern miracle" agents to the old pellet-type cats. In that comparison, the catalyzing agents and honeycomb structure are far superior and flow better. However, your OEM cat has exactly the same advantage over pellet-type cats.

    You're right on one thing, though, this argument is tired. You shout out the same "points" no matter what the discussion is about. Again you mention that these "high-flow" cats still pass emissions ergo they must catalyze as well as the OEM cat. But this would only be true if the OEM cat were right on the ragged edge of passing. In fact, with an OEM cat and a car in good running order, you will be way way under the state emissions requirements, even in CA. So just because a replacement cat will also pass the emissions requirement does not mean that it must catalyse as well. And what's wrong with making that point anyway? Just tell the truth, the "high-flow" cat doesn't work as well, but it flows better and works well enough to pass emissions. Isn't that a good enough reason for those who are interested? Why try to bs about how it's some miracle thing made of magic ingredients?

    And as far as hollowing out your cat, I'd bet a lot of people here could do it and still pass their state emissions tests. It would be cheaper, look nicer, and using your logic, it would catalyze as well as it did stock. If anyone ever looks in it and wonders why it's empty, you could pull an "emperor's new clothes" and tell them it was some magic catalyzing material that only smart people can see.

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