Wastegate spring v. MBC

Has anyone experimented with a new (stiffer) wastegate spring to raise their boost pressure, instead of going with an MBC or a hose bleed system?

My understanding is that the spring would be more accurate, and more reliable, although boost pressure would not be easily changed after the install. You would have to decide how much boost you were going to run, install the new spring at that calibration, and then leave it alone. None of that "two stage boost", or turing it up and down would be possible with the spring method (although I don't really understand why some of you turn your boost up and down anyway).

Thoughts? Comments?

It's certainly an option, and probably a good one for a track car that is run on high octane all the time becuase you're right, boost pressure will be more stable. Keep in mind that most people here have daily drivers that are generally fed 93ish octane most of the time.

However, the boost controller is there so that on tack night you can put your witches brew/toluene/race gas in and run more boost. Being able to tweak the boost infintely allows you to run the absolute maximum boost setting your car can deal with at the time.

Imagine putting that spring in on a cold day, then finding out on a hot day that it pings with that spring? That would bother me personally. You could then change the spring so it doesn't ping when it's hot out, but then when it's cold you aren't making as much power as you *could* be.

So basically, we move our boost up and down to keep things optimum for the current temperature, fuel octane, timing settings etc.

Hope this helps.

That's an interesting point about having to give up some potential power as a safety margin because of temperature change over the seasons. I expect that's an issue for altitude as well.

What would the difference in allowable maximum boost be relative to ambient air temperature?

Assuming that everything else remains the same (say, using 92 octane street gas and same altitude), how much boost would you have to reduce if the air temperature went from 0 degrees celcius to 30 degrees celcius?

Could you fix a ratio of, say, 0.5 psi reduced for every 5 degrees celcius temp increase? Could you also guess at a ratio for allowable maximum boost reduction in relation to altitude increase/decrease?

I really would prefer a "set it and forget it" option, and I like the spring idea, so I'm trying to guess how much of a boost safety margin should be built in for altitude and temperature change. Just as you say, I don't want to be pinging because of a spring that is too stiff. If we're only talking about 1 psi safety margin or something, I'd probably just live with it.

But I wonder how much that margin is in the real world. Your past posts indicated that you live in the Vancouver area, which is pretty temperate climate and mostly at sea level, but it's mountainous all around it. If you had set up your MBC for maximum boost in the winter rainy season at 4 degrees celcius, and then you wanted to drive the car up into the high altitude of the BC interior on a hot summer day six months later, by how many PSI of boost would you have to scale your MBC back to avoid pinging?

All of that is tough to calculate think, becuase while the temp goes up at the inlet of the turbo, that means the ambient air going through intercooler is also warmer, so it depends on how it effects both intercooler efficiency as well as turbo efficiency due to changes in air density, so you're working with several different variables at once.

Same goes for altitude correction, if the turbo compressor was linearly efficient, you could assign a specific vlaue to how boost pressure needs to vary, but it would change based on where you start on the map.
There's no real constant ratio because the efficiency of the turbo does not stay constant at different airflows.
Hopefully that made sense.
You'd basically just have to set it under worst case conditions and then be satisfied with that I think, or put out the bucks for an electronic boost controller. But reall a MBC like a g valve can be set and "forgotten" if you want, and most people find the boost spiking tolerable.

Another thing to search is www.autospeed.com, search for boost control. They have a variation of a G valve that is supposed to be more stable. I like the system personally but will not be trying it until my engine is broken in (temptation would be too great to just start flogging the thing. )

Ok, I appreciate the difficulties in developing a linear ratio. But let's take this down from the clouds.

From your actual experience, how high can you set your own MBC in winter driving at sea level, and how much do you crank it down when you set it in summer? What's the psi range that you, personally, have dealt with on your engine (assuming 92 octane gas)?

I have done 15psi on 92 octane on a cold day w/o problems. Usually when its warmer I run 13psi... With race gas she'll do 17psi at least.

14psi is my realistic limit on a warm day, running 93 pimp (sic, ha!) gas.

16psi will fly on 93 octane on a cool night with maybe some octane booster in the tank.

18-19 psi is no problem at the strip running 104 octane sunoco.

Boost is controlled by an HKS EVC II... I can set it to whatever I want at the time.

My delapitated 242ti (even more delapitated now- lol) varied about 4 psi as well. Didn't seem to care much about octane, on a cold day it would run 12 with 89, on a hot day it would ping at 10psi. :uhm:
It had numerous other issues/contributing factors to throw any of my data into the zone of invalid though. But on average (GROSS generalization alert!) you'll vary 5-4psi depending on a lot of factors.

My "up in the clouds" talk was an attempt at a logical explanation based on the physics of these things.
My "below the clouds" response is that a spring is no more accurate than a boost controller, since the "number" you see on your boost gauge is fairly redundant. It's a reference point for your own tuning, once you're tuned the to edge, you're there.

nd that's a lot easier to find with a boost controller. And it's a ball and spring valve, it's every bit as reliable as that rubber diagphragm in a coke can flexing in and out.
Unless you're having severe issues with boost spiking, why not have it adjustable? Heck you can "set it and forget it" if you want, you don't HAVE to change it.

Other than that my suggestion is to buy a tial or a deltagate and forget it.
:wink:

Let us know what you try!

Kenny,

From our relatively tiny statistical sample, correcting for 92 octane gas, we have a spread of only 2 psi between maximum boost possible under beneficial environmental conditions, and max boost possible under adverse conditions. This is the case for weezila (13 and 15 psi), bit jockey (14 and 16 psi with 93+ octane), and you (10 and 12 psi with 89 octane and poor engine tune).

So I'm not sure where you are drawing the evidence for your estimated range of 4 to 5 psi difference between beneficial and adverse environmental conditions.

I may yet use an MBC. I was directed towards the spring idea by the dyno shop I was speaking with, who recommended it over the MBC. This coming January, I intend to rent two hours of dyno time with air/fuel tracking, to see exactly what the effect of progressive boost increase on the engine will be. Very expensive investment for a 15 year old car, but I want the hard data.

Thanks all for the replies.

Well, it's going to range by more if you ever plan on running at the track. And 2psi is about 14hp. If not bothering to set your mbc is worth that to you, and you never plan on taking advantage of race gas, then sure.
But the spread increases largely if you start messing with fuel octane, whcih I was also factoring in.

Well, to throw a wrench in your numbers, I find I can run more boost on a 10C to 20C day than I can at 0C or colder. I have no trouble with pinging on a hot day at all, but it rarely gets above 30 in Calgary. The trouble I have is on a cold day, when the air is exceptionally dense. A couple weeks ago it got down to -20 and I was pinging at 8 psi, but when it was 30 degrees out this summer 15 was no problem.

I think the problem is with the K-jet that I'm running, which is only causing pinging because it's limited by the amount of fuel I'm putting into the engine. However, Kenny was running K-jet on his car and found that it liked colder air better. Make no mistake, my car likes colder air too - makes way more power for a given boost - but it'll ping at a lower boost pressure, too. I lose power on a hot day, but it's because of the less dense air.

Am I the only one who turns down the boost in the winter because of this? Is it because of my fuel injection? Because of the 3600 degree elevation of my home? Because of the particular turbo/intercooler combo I'm running (which is the same as many of you)?

By the way, I'm not driving the turbo anymore. It's been retired.

Well, to throw a wrench in your numbers, I find I can run more boost on a 10C to 20C day than I can at 0C or colder. I have no trouble with pinging on a hot day at all, but it rarely gets above 30 in Calgary.
:The trouble I have is on a cold day, when the air is exceptionally dense. A couple weeks ago it got down to -20 and I was pinging at 8 psi, but when it was 30 degrees out this summer 15 was no problem."

This is probably because the denser air is making you go lean, and the lean condition is making your engine even more prone to ping even with cooler intake air temps than with higher temps but adequate fuel.
So yeah, as I was trying to sya when I was "up in the clouds" there are way too many factors to reliably work out a "formula" that would actually be worth the effort to apply. The simpler formula is:
Not pinging? Crank it up.
Pinging? Crnak it down.


"However, Kenny was running K-jet on his car and found that it liked colder air better."

My engine most likely had a lot less power than yours though so I don't think it was going lean when it was cold out, so fuel mixture was not a factor for me. Only temperature. Where as in your case the fact that the denser charge made you go lean more than offset any help that the lower intake temps would have been.



"Am I the only one who turns down the boost in the winter because of this? Is it because of my fuel injection? Because of the 3600 degree elevation of my home? Because of the particular turbo/intercooler combo I'm running (which is the same as many of you)?"

I think it's just becuase you're going lean once the air is colder. If you had the fuel do deal with breathing those air molecules at a greater rate, the rest of the system would handle it.

"By the way, I'm not driving the turbo anymore. It's been retired."
The Junkyard B23ft?
Details? That is not good news for me.

First of all, I meant to say "3600 FOOT elevation", not some kind of sun-like temperature or multiple revolution spin... Just in case anyone was wondering.

Kenny - the hybrid is working fine, man. I'm so confident with it that I'm putting it in the wagon I'm building for my wife, albiet in a much more de-tuned state. I had to get out of the yellow car 'cause I just didn't feel safe anymore. Too much metal had rusted away in too many important places. Most of the suspension, brakes, and driveline will get stripped out and installed in the two other Volvos I have. The body is a complete wreck, and it's time to admit that.

I've moved into a pretty, navy blue, 1980 244. The car is completely stock, and VERY SLOW! I guess the 400,000 km and the big subwoofer box in the back have something to do with that.

3600 feet?!? Boy, you're far more up in the clouds than Kenny ever will be.

Matt,
Yeah, talked to Dale earlier and he confirmed the car was retired due to rust, not engine issues.
Relieveing. Heard it might go in the GT as well?
Back to a B21ft matt?

Matt,
Yeah, talked to Dale earlier and he confirmed the car was retired due to rust, not engine issues.
Relieveing. Heard it might go in the GT as well?
Back to a B21ft matt?

You heard it might go in the GT, eh? Well... that's soemthing Dale will have to convince me of. I think we'll be building a different motor for the GT, honestly. We were talking last night & it sounds like he wants to build a killer N/A motor for it. Sort of in keeping with the spirit of a GT, you know?

I think I'll have to feed him the 28/25mm IPD bars to shut him up about taking the hybrid, though!

B21FT, B23FT, B230FT, B23HP - I don't know yet. I need a car to put it in first - the blue car doesn't really fit the profile, you know? For this car I might keep my eye out for an Eagle Premier & a M46 equipped 264 for parts. A Megasquirted, 3.1 litre V6 should fit the character of a heavy, soft, sedan, huh? Anyway, that's all up in the air. The current motor is okay for now and it'll get me around until the wife's wagon is built. Then, we'll see.

Right now with colder air i can run 15 psi at 87 octane but summer i would ping at 14 psi with 94 octane...

Hey, maybe I am just confused, but what spring are you talking about? Are you talking about taking the wastegate actuator apart, and replacing the internals? Can you even do that?

As far as accuracy goes (and I will assume that to mean a consistent and steady psi level), I would think that the G-valve type of setup would be pretty accurate, and my experiences with it backs that up. When I built the valve, I used a bike pump to set it at 12 psi. It's been in for a long time now, and it gives me exactly 12 psi of boost every time, and no spiking.

If you want a better boost control, I would say that it is going to be electronic.

Greg

Ugly Duck said:

For this car I might keep my eye out for an Eagle Premier & a M46 equipped 264 for parts. A Megasquirted, 3.1 litre V6 should fit the character of a heavy, soft, sedan, huh? Anyway, that's all up in the air. The current motor is okay for now and it'll get me around until the wife's wagon is built. Then, we'll see.

Click to expand...

Sounds a little JohnLanish!!! Pretty slick I say