Big horsepower, why no porting? Benchracer discussion! ;)

[Aurora40]

I can understand the appeal of turning up the wick on a turbo car. For one it's really cheap and really easy. But once you go a little bigger, wouldn't some old fashion porting work make sense?

Just thinking out loud, though. But if you ported the intake plenum up to the heads, I'd think that would allow the cylinder to pull in more air at the same pressure level without being very difficult or expensive to do. Of course head porting would go even further, though then it may not be quite as easy or as affordable.

It seems like then you'd be more likely to support higher horsepower with the stock turbo and intercooler. I could be wrong, though. I realize the turbo still has to flow more air that way, but not at a higher pressure which I'd think would keep the heat down closer to stock levels. And once you want power levels that the stock turbo can't handle, you'd have had to upgrade anyway, but now you can still make more power without going much above stock boost levels.

Keeping the car closer to 1.6 bar would also keep it well within the control of the stock ECU and stock MAP sensor with a bit of tuning.

I believe you all have the secondary port butterfly in the intake plenum, right? On my car they are in the heads. So you could possibly really port out the secondary runners, put in a bigger butterfly, and it wouldn't affect part-throttle drivability or operation at all. With how rich the stock tune is, you might not even need to adjust that until you make more modifications. Though I have to say, I'd be a little concerned of upgrades if the stock injectors run at an 85% duty cycle from the factory.

Is there a reason no one does this? Am I making bad assumptions about the pressure/temp stuff? Are there actually little gains to be made from porting the intake plenum? Interested to hear thoughts or speculation.

Oh, I'd also be interested in if anyone upgrades the intercooler, or does anything like spraying the IC with nitrous or something to cool it down. It seems like the big upgrades are the exhaust and the boost. I was just curious if there's a reason for that.

[F1 LOTUS]

I think what you say is generally correct; the reason why people don't seem to go this route is firstly 'bang for the buck' and secondly it's not a simple 'bolt-on' modification?

[Houdini]

I can understand the appeal of turning up the wick on a turbo car. For one it's really cheap and really easy. But once you go a little bigger, wouldn't some old fashion porting work make sense?

Just thinking out loud, though. But if you ported the intake plenum up to the heads, I'd think that would allow the cylinder to pull in more air at the same pressure level without being very difficult or expensive to do. Of course head porting would go even further, though then it may not be quite as easy or as affordable.

It seems like then you'd be more likely to support higher horsepower with the stock turbo and intercooler. I could be wrong, though. I realize the turbo still has to flow more air that way, but not at a higher pressure which I'd think would keep the heat down closer to stock levels. And once you want power levels that the stock turbo can't handle, you'd have had to upgrade anyway, but now you can still make more power without going much above stock boost levels.

Keeping the car closer to 1.6 bar would also keep it well within the control of the stock ECU and stock MAP sensor with a bit of tuning.

I believe you all have the secondary port butterfly in the intake plenum, right? On my car they are in the heads. So you could possibly really port out the secondary runners, put in a bigger butterfly, and it wouldn't affect part-throttle drivability or operation at all. With how rich the stock tune is, you might not even need to adjust that until you make more modifications. Though I have to say, I'd be a little concerned of upgrades if the stock injectors run at an 85% duty cycle from the factory.

Is there a reason no one does this? Am I making bad assumptions about the pressure/temp stuff? Are there actually little gains to be made from porting the intake plenum? Interested to hear thoughts or speculation.

Oh, I'd also be interested in if anyone upgrades the intercooler, or does anything like spraying the IC with nitrous or something to cool it down. It seems like the big upgrades are the exhaust and the boost. I was just curious if there's a reason for that.

Good post!

Porting will make a nice difference. Why don't most people do it? Money is my reason right now but, I will get around to it eventually. it would be nice to see A to B comparison before and after porting with no other changes. An Engineer who used to work here and was the father of the "Disco Potato" GT2860RS did an A to B comparison on his 1800 cc MX-5. He gained 30HP - 35 HP after port matching and head work. That was wheel horsepower not flywheel so it can make for a nice increase.

The stock MAP sensor is only good for 1 bar of boost. To support more than 1 bar a 3 bar MAP sensor is required. 1.6 bar (23.2 psig) on a stock turbo is not going to happen. That turbo is not capable of that kind of boost without the turbine and compressor operating out of there effiency range. You need to upgrade the to another turbo all together or perhaps do the old hybrid trick using the stock turbine and t-bird compressor. Although that has been used by countless individuals to improve performance I don't think anyone ever taken the time to see if the turbine and compressor were a good match together. Just because it works doesn't mean it's a good match. The good thing about it is it allows a modification to the stock turbo without to much modification but you still end up with old technology. At least it's age appropriate for the age of the car.

The secondary throttle butterfles can be adjusted with other ECU's like the Haltech or you can do like some Isuzu guys have done and eliminate them all together. For a street car they have a real purpose and with modifications can be adjusted to suit the best opening rpm. I don't know why you couldn't extrude hone the intake manifold as you can with the exhaust and turbine housing for better flow and performance.

After upgrading the turbo for more performance you should also concider the following seriously. A better intercooler, possible cooling of the intercooler with a bottle or maybe better doing water injection form Augasquirt. You'll need a better radiator as well because increasing the horsepower will put a larger load on the cooling system and our radiator is not that big. If you go beyond a certain horsepower level you'll need to change out the clutch for a heavy duty one and a Quaife LSD is not a bad idea to get the power to the ground and improve your cornering ability. Now that your going real fast you have to upgrade you're brakes as well and thanks to Brian that is doable as well. Don't forget engine management with Haltech or Mega-Squirt, or ?

Lot's of ways to make it better and I know I left out some things. Just bring your check book. Horsepower isn't cheap and high performance modifications will give you high performance headaches!

[Aurora40]

The stock MAP sensor is only good for 1 bar of boost. To support more than 1 bar a 3 bar MAP sensor is required. 1.6 bar (23.2 psig) on a stock turbo is not going to happen. That turbo is not capable of that kind of boost without the turbine and compressor operating out of there effiency range.

Ah sorry, it seems everyone here speaks absolute pressures. 1.6 bar of absolute pressure, or .6 bar of boost.

I'm assuming swapping in a new turbo isn't super cheap, though perhaps it is. I wouldn't think just porting the intake plenum would be too expensive, but I dunno.

I guess what I was thinking or wondering is that there's two ways to get more air into the engine. One is to up the boost, and one is to have the motor breathe better at a given pressure. Or of course to do those in combination... Seems everyone goes the boost route. I'd think there would be some downsides including increased intake temps (and thus more risk of detonation etc) that you wouldn't have with increasing the breathing of the engine. And it seems like if you stay closer to stock boost levels you could use most all of the stock boost control mechanisms as well.

As an aside, my impression of extrude honing is that it's useful for complex passages and such. But it also seems to be a bit pricey, and it wouldn't result in a good match where the ported plenum meets the stock head passage. I imagine that the porting could be done by more traditional means for a lot less, though I can't say I've ever seen the Elan plenum off a car.

Lot's of ways to make it better and I know I left out some things. Just bring your check book.

LOL, tell me about it! It seems any upgrades for my car cost a small fortune. It's definitely not the cheapest way to go fast, but it sure is fun.

[Houdini]

I agree that extrude hone is expensive. Never tried it myself but they and I'm not sure it's worth it on a street car. Our race car had it done with good results but then we're talking a race car.

New turbos aren't cheap if you pay retail ($1100 for a ball bearing turbo - more for an IHI), but porting and such requires removal of the head, manifolds, turbo, etc. It can be pretty expensive because you're more than likely paying someone else to do it unless you have your own machine shop.

There have been day's I wish I had just stayed stock because one thing just snowballs into another and at some point you can't turn back very easily. It sure is fun though, and I would do it all over again.

[F1 LOTUS]

There have been day's I wish I had just stayed stock because one thing just snowballs into another and at some point you can't turn back very easily. It sure is fun though, and I would do it all over again.

When?...When?...will we ever learn

[Ashaman]

One reason is cost. You can literally do the whole T-bird swap in an afternoon & as cheap as $100 (Ebay - they aren't a very hot item). Like Houdini said though, nobody seems to know if it is a good "match" or not. I personally used the whole turbo, and I did notice the compressor LOOKS much bigger visibly...

The "common wisdom" of the turboford crowd was that 20 PSI was pushing it for those units. In stock form they developed 15PSI, so I would imagine the engineers allowed for some margin, but 1.6 bar is a long way to go, so I seriously doubt even they are up for it!

I have no idea, but apparently some disagree that bigger is better, or that smooth is better than textured. As a result, I didn't do any port work (on the intake side) because I am not convinced of the work/cost payoff ratio is worth it. Further, I have read so much conflicting information that I was concerned it might not net a power gain at all.

I think in the past there was some discussion on this topic, where sometimes having the intake tract too smooth or large hurt performance? I seem to remember this counter-intuitive information; so maybe someone can chime in if they remember why. There is some info on it that expalins here though:

http://www.mototuneusa.com/think_fast.htm

So for me: extrude hone was way too expensive+I was out of my league getting into this+I did not know of anyone to go to for solid advice=leave well enough alone!

[F1 LOTUS]

If what the Mototune man says is true (quite likely), then it seems like the majority of the tuning industry are ignoring basic principles that have been well established for half a century or more?
When I was doing this kind of work, more often than not stock intake ports were already too big although they could still benefit from reshaping. Some were so big and bad we actually filled the ports in with weld! When using the flow bench, port velocity was carefully monitored as well as flow, and there were some tricks to 'spoil' reverse flow too - Old school stuff!
I think it is quite well established that a forced induction engine will respond to 'conventional' tuning the same way a naturally aspirated one does, actually better, because you should be able to optimise off-boost conditions without fear of strangling the top end as you now have a fan stuffing the air in at higher revs?

[F1 LOTUS]

This is a very good article that covers some of the 'old school' stuff I was prattling on about...
http://www.beautyofspeed.com/data/cylinder_headtech/

[Aurora40]

Well certainly just porting stuff out until you practically cut through it isn't the way to go. And it's possible the ports are big enough already. You won't know until you try it.

But that article is pretty ridiculous. He seems to imply everyone just goes nuts for the biggest flowbench numbers they can get, and then that's it. I think most people when they do work like that will do a lot of dyno testing to see what the changes do.

It just seems very hypey. Obviously there are many examples where larger ports = larger power. I mean, if you took his statement in the same basic way and trimmed out any context, then why not fill your ports in? The less they show on a flowbench, the better, right? Maybe just put a toothpick in the port hole, then fill the rest in with some JB Weld or something.

This guy is basically dumbing down arguments to the contrary in order to defeat them. Perhaps in the case of the motorcycle engines he's worked with, smaller ports work better. That doesn't make it a universal truth. Nor is saying larger ports are better.

I'm not trying to say what works and doesn't, I've never had or worked on an Elan. I'm just wondering why no one seems to try it. As I said, I am curious. I wonder if it's just the unknown factor, or that there are better or cheaper options, etc.

[F1 LOTUS]

I'm not trying to say what works and doesn't, I've never had or worked on an Elan. I'm just wondering why no one seems to try it. As I said, I am curious. I wonder if it's just the unknown factor, or that there are better or cheaper options, etc.

I believe there are a lot of factors why people aren't doing this, ranging from lack of experience, equipment, time? Also, there doesn't seem to be a proven example to follow or inspire and the limited production numbers of our car means there's no industry offering gas-flowed heads on an exchange basis unlike more popular engines? For most people it's possible to simply bolt-on enough power to take them to the point where more 'serious' upgrades become neccessary - clutch, diff, ECU, injectors etc...

[Dave M]

A little late to the party on this one, but thought I'd throw in my $.02 after having had a similar discussion with my engine tech guy a while back. When I had the engine out, I thought "what a great time to port things". However I ended up "flow matching" the head instead (which *did* involve some porting). This involved balancing the airflow into the head with the airflow out. The key here is to optimize flow rather than maximize it. It was explained to me that you could port and increase flow, but without changing the way the valves open to let air in and out, it may make no difference whatsoever. Sure, you can then start looking into different cams, but IMO who wants to spend that sort of money to reinvent the wheel. If you change valve openings and cam profiles, get ready for lots of work. Plus, you will change the way power is made in the car. It can be tuned for high horsepower in a narrow rpm band this way, but does someone want that for a street car?

That's why I didn't port for porting's sake. Bascially there are other ways to make power that don't cost nearly as much or require the technical expertise.

[Doc Fizzix]

This is a good thread! There is some reall good information here. I would recommend that you guys also look on the Isuzu site http://www.isuzone.org/forums/ they have discussed this several times and also have a ton of great information on this subject

[Philbo]

I can understand the appeal of turning up the wick on a turbo car. For one it's really cheap and really easy. But once you go a little bigger, wouldn't some old fashion porting work make sense?

Just thinking out loud, though. But if you ported the intake plenum up to the heads, I'd think that would allow the cylinder to pull in more air at the same pressure level without being very difficult or expensive to do. Of course head porting would go even further, though then it may not be quite as easy or as affordable.

It seems like then you'd be more likely to support higher horsepower with the stock turbo and intercooler. I could be wrong, though. I realize the turbo still has to flow more air that way, but not at a higher pressure which I'd think would keep the heat down closer to stock levels. And once you want power levels that the stock turbo can't handle, you'd have had to upgrade anyway, but now you can still make more power without going much above stock boost levels.

Keeping the car closer to 1.6 bar would also keep it well within the control of the stock ECU and stock MAP sensor with a bit of tuning.

I believe you all have the secondary port butterfly in the intake plenum, right? On my car they are in the heads. So you could possibly really port out the secondary runners, put in a bigger butterfly, and it wouldn't affect part-throttle drivability or operation at all. With how rich the stock tune is, you might not even need to adjust that until you make more modifications. Though I have to say, I'd be a little concerned of upgrades if the stock injectors run at an 85% duty cycle from the factory.

Is there a reason no one does this? Am I making bad assumptions about the pressure/temp stuff? Are there actually little gains to be made from porting the intake plenum? Interested to hear thoughts or speculation.

Oh, I'd also be interested in if anyone upgrades the intercooler, or does anything like spraying the IC with nitrous or something to cool it down. It seems like the big upgrades are the exhaust and the boost. I was just curious if there's a reason for that.

As has been said, it depends where the easy gains are. If you get involved in porting then you really need to do a proper job on both intake and outlet. That's quite a significant block of work. I know of only one person who has undertaken head porting work on an Elan, and that was part of a monster engine rebuild. It's the kind of thing that's towards the end of a list that starts with new exhaust, new turbo etc.

Also, if you change the flow characteristics then you probably shouldn't be keeping the stock maps etc as they will go lean (more flow at a given boost than they allow for). So really porting would be done as part of a ne w ECU operation, at which point you've already gone for a new turbo...

As regards the secondary butterflies, they are REALLY restrictive on flow in the midrange. On my car (remapped with a Haltech) we've controlled the butterflies to open much earlier and the transformation is amazing. But you do lose a little driveability.

Overall, porting is A Good Thing, but due to the difficulties it tends to be done once "easier" things have been done. Many of us are "happy" with the performance as it is at around 240bhp wheel...it's easy to think that there's more performance to unlock within the engine but how much are you prepared to spend to get it?

Philbo