planedrop

Before I even say what I am going to say, I would first like to ask that you please don't leave sarcastic comments regarding this. If you don't have something to add to answering the question then please don't at all, and I know in a sense buying a 951 maybe makes the most sense here, but wanted to ask something anyway.

So I have a 1983 944 NA, and I love the thing dearly, it's in incredibly good condition and I am replacing all the older parts with new ones (by the end of the year most things should be essentially like new), but I do indeed want more power out of the thing, and I don't have the money for a 951 right now and honestly, by the time I have that cash I don't want to have all the hard work into this one thrown away so to speak. So I know making it faster by turboing it or something like that is just completely dumb so I won't do that.

But I want to know if rebuilding the engine, porting, polishing, etc... and boring it out (hope I used the right term there, still a car noob honestly) to a 2.7L or 3.0L is realistic. Can this be done safely? How much would it cost for a engine shop to do this (roughly, I know this varies)? How much power can the Audi (I was told the non turbo's are an Audi transmission) transmission take? How much power might the rebuilt engine put out? Can the rest of the car take this? What other parts might I have to replace? Is it still safe to use as a daily driver in this case, or would it be substantially more likely to have issue, even if done professionally?

I really want to keep this thing for a quite a while, the condition is amazing, and honestly I like the consistent power of NA engines better for the most part anyway so having a faster NA would be nice. Thanks for any help on this, and again, if you don't have something to add about it please don't reply, had bad luck on here last time I posted about making an NA faster, not asking if a 951 would be better, asking if I can rebuild an NA engine to be faster.

CVR_Rally

Ah the quest for more power.

There are some things to consider if you tried to enlarge the bore of the 2.5L such as the change to the characteristics of the air/fuel mixture, the DME's ability to handle the change, and of course the material that the cylinder walls are made from is special.

Porting/polishing might not be a bad idea and you may also want to have the injectors sonically cleaned to bring them back to full spec. Another possibility would be to have the head shaved a little to increase the compression ratio. I've not had it done but the guy I've been getting some 944S parts from has the same year/model and he did this for a little more power.

Another possibility would be to go with a MAF conversion. I would do any of those before enlarging cylinders.

Good luck!

Chris

harveyf

Planedrop, respectfully, I would submit that the 944 was never about straight line speed but more so handling in the curves. It is pretty well understood that getting more than a 10% -15% horsepower increase out of any N/A engine is going to represent time, money, and probably frustration as you transform a reliable car into a finicky bitch. If you have an 83 in incredibly good condition, my goal would be to preserve it in excellent stock condition, as good stock cars are getting harder and harder to find. Enjoy it the way it came from the factory. Go find some corners to carve.

BTW, my F150 2.7 litre dual turbo Eco-Boost has amazing acceleration and power. Turbo's are magical

harveyf

One other thought. Your 944 N/A engine is making its best horsepower up around 5500 rpm. It starts to tail off as you reach the redline. So you'll get the best power and the best "sensation" of power if you are willing to spool your engine up to 6000 rpm or so as you accelerate. (Engine noise = sensation of speed). It also helps to have the windows rolled down!

I've noticed some folks are reluctant to take their cars up to the redline. Maybe they think they are hurting the engine. My track car, which has a very stock engine, lives at these rpm ranges. I think that after you perform a good quality rebuild to stock specifications, you should be very comfortable running your car at 6000 rpm all day long if you want to. That is one of the benefits of your doing a first rate rebuild.

Reviewers "in the day" would generally comment about European cars that you had to "work the transmission to stay in the power band". All they mean is that the European cars, having smaller displacement and thus superior fuel economy, didn't have the gobs of low end torque that big old American V-8s provided. Not a bad thing, just a different design aesthetic. But that remains the way you need to drive these cars in order to realize their full potential.

I am now returning to my cave high on the mountain side and will continue to contemplate my navel when not surfing Rennlist

odonnell

This is the potentially the most common question ever asked on this board...do a google search, you'll find what has been said on the topic. I gauruntee you there are 100+ applicable search results. There's only so much you can do with a NA 8v 2.5 i4 engine - report back when you decide what mods you are going to do.

ramius665

Comment of the day for sure.

V2Rocket

You can only really bore the engine out to 2.7L. But you might as well just buy a factory 2.7L engine at that point.

The easiest way to a 3.0L NA engine would be to start with a 2.7NA engine, fit a 3.0 crankshaft and get aftermarket connecting rods and pistons to fit.

If you are getting aftermarket pistons, you could actually start with a 2.5 block and just bore to fit. The cheapest I've ever seen quality Alusil bore/etching service is ~$300 for a 944 block. Off-the-shelf "stock type" Wossner (Alusil-compatible) pistons are ~$650/set, custom Wossners are ~$1000.

The NA head (2.5 or 2.7) flows enough for probably 200HP. With a 1985.5-1988 camshaft I would expect ~200hp to be the cap for a 3.0L 8-valve NA, without porting the head. Polishing doesn't do anything. It would be a sweet, torquey engine with a nice top end. A hotter camshaft (WebCam, Elgin, Paeco, or Milledge) might get you some more on top of that but then you really would want to have a 2.7L head for the extra flow potential.

Aside from that, a "factory rebuild" is almost $2000 in parts alone.
So add that to the cost of your pistons/rods/crankshaft/machine work.

Browar

Hi,
I am doing what You are thinking of.
My engine is torn apart for power-quest.
I like my NA very much and don't want to swap or turbo it.
Also my car will be still street legal. Hope to come back with reply in late summer.
What realistic power figures we are looking at? 180ps... Would be nice... 190ps very, very happy... Anything more - amazing...

planedrop

Thanks for all the help everyone, I've gotten some good answers here, I will try and reply to all of you with this one reply so look for you name at the beginning of the paragraph. But first for a couple more questions to ask all of you, first off how much HP does a NA 944 put out anyway, I seem to get two results on wikipedia, there is a chart that shows for years 82 to 87 you get 163HP, but then below that, in the same year section it shows 143HP for 85.1 and older and 147HP for 85.2 and newer, so which is it lol? Also, would maybe an option be using a 944S or S2 engine, find a wrecked one, do a rebuild on that engine without boring (especially on the S2 since it's already 3.0L)? I mean would the Audi transmission handle up to 200 or so HP reliably? One more question for everyone, would going with 3 inch headers, and a 3 inch exhaust with a high flow CAT help at all? Is it worth the 1500 from Lindsey Racing, an will it even pass DEQ with that CAT? Thanks again for all the help everyone, determining my long term plans with the car right now!

CVR_Rally: alright this makes sense, how much would a head shave cost from a professional shop do you think? And would that likely take more than a week ish, it is my daily driver so the reason I asked about reliability earlier as well is because I need to be able to use it as a daily driver lol. Makes sense though, maybe I should do everything I can to the engine WITHOUT enlarging the cylinders. Also, what is a MAF, I have heard this term a lot but I'm not exactly sure what it does, I believe it stands for "Mass Air Flow" right? Thanks again!

harveyf: Yes I know they aren't built for super high straight line speed, I prefer corning in a car anyway, but still having a decent amount more power would be pretty awesome. I'm not a muscle car guy or anything, but I do feel that 143hp is a little lacking even on such a lightweight car, closer to the 200 mark would make more sense IMO, and I know they delivered this with the 951 and 944S. Also, even a 15% HP increase would be nice, I love the handling of the car very much and won't have the money for something like a 951 for a while anyway, but if I can do a lot of small things to make this one a bit faster I would love to. Also, I am willing to run it to the 6000RPM redline, love doing it all the time, I feel it's a Porsche designed for racing, if it wasn't designed to take redline all day, then it's not a race car lol. But yeah, I think getting even another 20HP or so out of it would be a nice thing, and if I can get closer to 190HP or 200HP that would be ideal! But again, needs to be reliable as well.

odennell: I understand that there are other threads out there about this, but I posted my own because I want answers to all my questions, not just is a rebuild possible, etc... I tried searching for a bit before hand but couldn't get it all answered, so figured I would post because the discussion is fun, at least I think for most of you, anyway.

V2Rocket: So maybe getting a 944 2.7L engine or a 944 S2 3.0L engine would be a better/cheaper option for more power? Or should I just stick with my NA 2.5L and make it tip top shape with maybe closer to like 185 to 195HP? Say I did have this one changed out to a 2.7L, are we looking at maybe 4000 to 5000 dollars? To me that's still cheaper than a 951 by a lot, and I love this cars particular condition, color, and the small amount of issues it has, so keeping it is honestly something I have already decided. I could find a wrecked 944 S, S2, or 944 2.7L maybe, and use that engine, only thing is would my Audi transmission handle that? I know it's a good transmission but still nowhere near as good as the 951 transmission, at least from what I have gathered. Starting to think an engine from a wrecked car would maybe be the better option, considering it's my daily driver and I don't want to be without it more than a week or two at the most. Thanks for all the help!

planedrop

Sorry, forgot to add the reply to Browar to the last post, so here ya go! That is very nice man, I hope you post about it later this year and let us know how that goes, would be very interested. I probably won't be doing mine until the summer of 2017 as then I will be done with college and the car should be in like new shape by then, this year is all about getting it aesthetically, and mechanically as good as possible.

V2Rocket

The European 944 from 82-87 had 163HP.
The US 944 from 82-85 had 143HP.
The US 944 from 85.5-87 had 147hp, due to the camshaft change.
US 1988 944 was ~152-155 HP due to higher compression and a tune change.
US 1989 944 was 2.7L, about 162hp. Highest compression of all 944 models.

You need to get a MAF or MAP conversion before anything else if you want to make more power from your NA engine. The Stock AFM just will not cut it.

With a MAF conversion, some tuning, and a 2-degree advanced cam I took my engine from 143hp to 160 and it was awesome.

At that point I felt the early camshaft was the limiting factor, along with the "low displacement". A hotter camshaft would be a good choice there, but I don't know how the aftermarket 944 cams affect emissions testing.

A 3.0 S2 engine swap would be the best way to top 200HP, you just have to sort out some wiring differences, if you get the rest of the engine complete.

planedrop

Thanks for the info! That makes a lot more sense to me now, I figured it was 143 for my car, makes sense now.

What exactly is a MAF? I have heard the term many times but don't totally get what it's goal is, so please explain if you can. Makes sense though.

I see, well even 160HP would be awesome, I would hope for more like 180HP with all the other things I wanna do to it. Also, would doing a 3 inch exhaust with 3 inch headers make a good difference? Lindsey Racing sells one and it comes with a high flow CAT ( would have to make sure it's a good enough one to pass emissions though first), but for 1500 I'm not sure if it's worth the extra power.

Maybe I will try and get a lot out of this engine but not go completely crazy, and eventually try and find a S2 engine, rebuild it, and swap that in.

art

The MAF conversion made a big difference to the car, much better to drive.

One way to think about these engines, they are 1/2 of a 5 liter mustang. If you multiply our power by 2, you get a 300 hp 5.0 V8 which is pretty stout for a mild engine. They get 400 hp from mods like better flowing heads, higher cam lift, etc.

Read up on what the Ford/Chevy smallblock guys do the get more power, the bore and combustion chamber of the 944 is almost the same as a 350 Chevy.

Also keep in mind that adding large amounts to the peak power will usually result in compromising other parts of the powerband.

odonnell

Some literature on AFM vs MAF: https://splitsec.com/wp-content/uplo...Conversion.pdf

It's a BMW product but you'll get the overall gist of it, if you're ok with technical content.

TL;DR the AFM is physically restrictive and limits tuning. The stock tune also was made in an era where even American sports cars sucked because of the gas crisis. I've run multiple tunes, including stock, Rogue NA-Tune (MAF) and my own homebrew speed-density (MAP) setup. Stock is lackluster.

V2Rocket

No, there isn't any reason to go larger than stock exhaust size on an NA car (even an S2). All it will do is make the car louder, and slower at the bottom RPM range.

I have a small section of my exhaust system that is actually SMALLER than factory (2" OD instead of 2.125" or so) and I credit that change for a large jump in torque that my car has versus a "factory-rated" 944.

With my car in 160hp tune it was making 165 lbft torque, where the factory rating was 137. So my 2.5L low-compression mild camshaft engine was making as much torque as a 2.7L high-compression 1989 engine did.