Grsmonkey's Turbo build (updated 10/10/09)

[Scottinva]

Good looking numbers Grsmonkey!

At what boost level would you say 91octane is at its limit to make decent power? I was just curious because that is what im tuned on and plan to continue tuning on, though we do have 94oct somewhat readily available at some gas stations here every station has 91, which is important to me since I want to DD the car and not worry about where i'm going to fill up.

Again, sweet numbers!

That stinks, 91-93 is normal, some stations have higher here in va.

[George]

With evety bump between 9-18psi I saw an increase in my 60-120 time.

That is the best example of HP determination and engine efficiency that I can think of, congratulations.

I see the error of my thinking. The M30 with a log manifold can take 30 psi easy.

Carry on.

Short of bench testing or performing computation flow analysis on the manifold what more would you like than a comparison of intake manifold pressure increases vs easily repeatable performance times? Huh? I'm really curious Duke.

You seem to shit on others' empirical evidence but offer your experiences as the the one and only truth.

With your infinite wisdom and engineering degrees why don't you show us the multitude of compressible flow calculations performed on specific log manifolds vs. tubular manifolds (on the M30 head)?

[BadM535i]

[Shadow]

Dang, so the m30 won't make much power past
14-22psi? That sucks!

14 to 22+psi not much of a power increase.
Head is a major restriction.

j/k

[Scottinva]

I learned a long time ago not to disagree with this bunch, on the topics presented. Many have engineering degrees, others have many years as technicians. It's just better to listen to what they are saying, because they speak the truth. So I advice you do the same Duke.

[Duke]

It's just better to listen to what they are saying, because they speak the truth.

I agree, these guys know their $hit. I bow to them. I am a sponge and they are my water.

Please educate me further all of you that have BTDT.

[T_C_D]

This is the best example I have. Same engine, same dyno 60 days apart.

1 bar spring and 1.3 bar spring. No other changes.

+4.41psi = +48rwhp and + 56rwtq

Efficiencies are probably deminishing at these higher boost levels but it's still worth adding the boost. This particular engine had about 212k miles on it at this point so it's hard to tell how much of the boost is blowing by the rings.

[FirstFives Dictator]

I think the reason people think these cars stop flowing at higher boost levels is they keep thinking arithmetically instead of geometrically.

Gas flow proportional to sqrt of ratio of pressures.

Just for fun I took sqrt 1.3/1 = 1.14 which is sqrt of the ratio of (new boost)/(old boost)

1.14 * 343.25 = 391.305 which is pretty close to the dyno sheet reading of 391.14 (well Todd's 99.96% there, anyway)


Sounds like nature has not yet broken down yet, unless I'm missing something with the math.

[Jeremy]

Wait, whut?

Seriously, Peter, I don't doubt you, but teach me something here. Why is the power increase from more boost not linear? I always thought of it as linear, I never considered the possibility that it might not be so.

I knew the head would start to flow less efficiently at a certain point, but I guess I didn't realize that the power gains from boost followed an exponential curve.

As an example, say base hp for the motor is 200 hp. You then add 10psi and get 250 hp, a 50hp increase. Doubling the boost to 20psi using the linear method, one might expect 300hp. You're saying the expected hp from doubling the boost in this case (all things being perfect) would be 271 hp?

sqrt(20/10) * 50 = 70.7

Jeremy

[FirstFives Dictator]

Wait, whut?

Seriously, Peter, I don't doubt you, but teach me something here. Why is the power increase from more boost not linear? I always thought of it as linear, I never considered the possibility that it might not be so.

I knew the head would start to flow less efficiently at a certain point, but I guess I didn't realize that the power gains from boost followed an exponential curve.

Jeremy

I think it's because the charge flow is not linear with boost but proportional to the sqrt.

Surely someone can check my work here; I'm not saying I have to be right, but it's freaky that the #'s are so close.

[Jeremy]

I ninja-edited my example, sorry.

[FirstFives Dictator]

I ninja-edited my example, sorry.

Certainly Todd's car fits' the curve perfectly.

When you talk about some heads flowing better (4 valve) than others, I just think that better flowing heads start with better flow at same boost levels and are farther down on the sqrt curve than heads that don't flow as well.

I think ram effect etc, not counted, basic flow (I'm really simplifying what happens in a turbo intake; I'm even understating how much I'm simplifying it) should be proportional to sqrt of pressures.

[M. Holtmeier]

I would be more concerned with heat soak after several runs. I would check the temperature of the intercooler radiator after 2 runs.


Mike, a couple of questions:

Are you running straight water or water/meth?

Do you have coolant in your intercooler system or just straight water?

I think your timing is limited by burn rate at that pressure. I only have 91 octane available as well. I keep to 9psi for regular street driving.

Washer fluid was what I was injecting. The IAT was ~100 before each run if I was using the water or not. ECT was ~190 before each run, never crept up or anything like that. I have an A/F mix in the intercooler to protect to ~+20F and water wetter additive. There are the 2 stock TCD heat exchangers in a sealed box with elec fans and 2 addl' exchangers on the front to catch open air.

Back in '07 when I running the setup with the stock b34 at 200k I had the boost set to 20psi and remember there being stations with 93. According to the dyno op the stations hadn't switched the octane tags and swore that everything was 91 at that time as well. The car hauled ass, though never put on a dyno, I tore everything up but the engine. I should mention again that at 20 psi with the stock b34 long block, I was able to run the stock ign system and stock fuel pumps. With the b35 head, I ran out of fuel at 15psi, installed a 255lph in tank and then had the spark blowing out at 13-15 psi. The MS datalogged over 7 runs anywhere from 15-18 psi. The dyno showed as high as 22. If I really was running 22 psi on the dyno, that's probably half of the problem right there. I just borrowed a handheld 0-30psi pressure gauge from a friend, going to hook that up tomorrow and see what's really going on in the manifold.

At what boost level would you say 91octane is at its limit to make decent power?

I really can't say right now. It put down 350 at 15psi with 15 degrees of timing without w/i, but the dyno op ssaid he started hearing det. I ran it out to the rev limiter and didn't hear a thing. I might pull the valve cover and see if anything is up. The car runs great though, I have the timing at 13 deg and it's giving me 335/375 at the wheels.

[George]

Hmm, report back with your findings on what the actual intake pressure is.

I'm curious as to how the dyno was measuring manifold pressure?

[Scottinva]

So generally a twin cam can flow better, however a well designed single cam has the potential to be just as efficient? People complain about the head, however I don't see how it's such a big concern. Bmw really went out of their way to make the single cam work good.

[FirstFives Dictator]

So generally a twin cam can flow better, however a well designed single cam has the potential to be just as efficient? People complain about the head, however I don't see how it's such a big concern. Bmw really went out of their way to make the single cam work good.

No, for HP, the twin cam is more efficient. But both have to obey the same gas laws.

Boost on the 2 valve motor doesn't 'stack up' or anything like that. Turbo owners just use them at a higher points on the boost vs. flow curve than twin cam owners (4G63 etc)

[Brad D.]

No matter how good a two valve head is, there is always a limitation in valve curtain area when compared to a four valve head. Plus, the head design can be more efficient (pent-roof) than that in a 2 valve head with large valves (i.e. valve/wall shrouding). You would be hard pressed to ever get even a worked over two valve head to out perform as well as a well designed four valve unit.

[Scottinva]

Okay, I understand more know. I was wondering if a very well designed 2 valve head, could possibly be more efficient than a less well designed twim cam head. I would think at higher RPM the twim cam would shine even more so, due to the fact of less moving parts. There is less "flex" within the valvetrain, which I would think would outperform the single cam. I understand that generally speaking twin cam is more efficient, but could a properly ported and worked over m30 head, outflow a stock head in another cam maybe?

[FirstFives Dictator]

No matter how good a two valve head is, there is always a limitation in valve curtain area when compared to a four valve head. Plus, the head design can be more efficient (pent-roof) than that in a 2 valve head with large valves (i.e. valve/wall shrouding). You would be hard pressed to ever get even a worked over two valve head to out perform as well as a well designed four valve unit.

agreed. All things equal, I'm guess Mike's 20psi power could be as much as 140% of his 10psi power. If not limited by detonation etc.

[Brad D.]

Okay, I understand more know. I was wondering if a very well designed 2 valve head, could possibly be more efficient than a less well designed twim cam head. I would think at higher RPM the twim cam would shine even more so, due to the fact of less moving parts. There is less "flex" within the valvetrain, which I would think would outperform the single cam. I understand that generally speaking twin cam is more efficient, but could a properly ported and worked over m30 head, outflow a stock head in another cam maybe?

I really wanted to know how much different m30 cyl heads flow! How much better is the m30b35 head? How much difference does professional porting make? So I decided to find out.

Since I moved to OH I had no contacts for a nachine shop so I decided to introduce myself to some fo the local shops and see what they said. TC Kline recommended a shop called ARJ Enterprises. They build the race engines for TC's World Speed Challenge cars.

I take a ride out to their shop. The shop is a barn type building behind a farm house. But inside is a full machine shop with a flow bench and an engine dyno! All this just 6 miles from the TCD Worldwide Headquarters!

I paid to have the shop build a jig for the m30 cyl head so it could be flowed. I picked up the cyl head an results for the m30b34. This cyl head received a $660 "Stage 3" porting job from a shop in TN that is used by Turner Motorsports. This is the head that was on the 745i that produced 331rwhp/316rwtq. Presumably this head flows pretty well.

At .4" of lift it flowed 169cfm on the intake valve and 134cfm on the exhaust valve. For comparison a stock S50 head flows 233cfm on the intake side at the same lift! That's 38% more for the 4 valve head!

I have a stock b34 and stock b35 head for him to flow as well. I report back when I have the results.

Todd

Update. I had the stock cyl head form the 325i flowed. At .400 it flowed 162cfm on the intake and 121cfm on the exhaust. Keep in mind that the m20 has 4mm smaller intake valves and 2mm smaller exhaust valves. Despite this handicap it flowed 96% of the ported m30b34 head on the intake and 90% on the exhaust side!

From this thread.

That right there proves my point. Even a worked two valve head can't even touch a stock s50 head (not that different from an m50 head). Plus as you increase valve size in a two valve head to increase curtain area, you wind up with a new set of problems like valve shrouding. There is no way a 2 valve head will ever be on the same playing field as a 4 valve head. Now, that is not to say you can't make good power with one, but all things being equal that engine would theoretically make more power and potentially be more detonation resistant with a 4 valve head.

On another note, lets not clutter up Mike's thread with slightly unrelated discussion unless he's ok with it.

[turbodan]

The key word is efficiency. Four valve heads will fill the cylinders more efficiently for any given boost level and resist detonation far beyond the limits of a two valve head. Two valve motors require lower compression or better fuel to run similar boost levels.

That doesn't mean you can't make power with a two valve motor, but it would be easier to do with a four valve motor. The head just sees a pressure ratio. As long as you maintain a favorable intake/exhaust pressure ratio, cylinder filling wont be affected by increased boost pressures. Squish area, combustion chamber design and compression ratio are much more critical for a two valve motor. Probably more than flow capacity. As long as you're using a properly sized turbo and capable exhaust manifold you'll be able to fill the cylinders. Eventually, you'll run up against detonation. Four valve motors come out ahead there every time.

[FirstFives Dictator]

At .4" of lift it flowed 169cfm on the intake valve and 134cfm on the exhaust valve. For comparison a stock S50 head flows 233cfm on the intake side at the same lift! That's 38% more for the 4 valve head!

That makes sense. The 4 valve head starts off with much more flow but should follow the same gas laws as boost build.

Sorry Mike; I owe you a thread cleanup.

[turbodan]

Despite this handicap it flowed 96% of the ported m30b34 head on the intake and 90% on the exhaust side!

Keep in mind, folks, thats a stock M20B25 head VS a "Stage 3" M30B34 head. Stock for stock, giving the port job the benefit of a doubt, the M20B25 head would outflow the M30B34 head.

How about that.

[Scottinva]

Despite this handicap it flowed 96% of the ported m30b34 head on the intake and 90% on the exhaust side!

Keep in mind, folks, thats a stock M20B25 head VS a "Stage 3" M30B34 head. Stock for stock, giving the port job the benefit of a doubt, the M20B25 head would outflow the M30B34 head.

How about that.

I would think the comparison between the m5 and m30b34 head would be more relevant. This is due to the fact of same manufacturer, and same "era" of the head. Also a bit more offtopic would be how the ITB affects it.

[turbodan]

The subject of my post isn't 12v VS 24v, its how awesome the M20B25 head is.

We've already pretty clearly established the advantages of a 24v head.

[Scottinva]

The subject of my post isn't 12v VS 24v, its how awesome the M20B25 head is.

We've already pretty clearly established the advantages of a 24v head.

The advantages are very clear, however how much they affect, is harder to grasp.

[T_C_D]

A stock s38b35 head flows slightly less than a stock m50xx head. I don;t have the exact numbers written down.

[turbodan]

The advantages are very clear, however how much they affect, is harder to grasp.

I dont see how that matters. How much they affect what? Detonation is still the limiting factor for either engine. You can still make ridiculous amounts of power with either engine. A 4 valve will make a little more of the same displacement on the same fuel, but who cares.

[M. Holtmeier]

So I found out the signal line to the MS is "leaking off" a little. My boost gauge in the car is inline with what the MS sees. The 15psi I thought I left the dyno with is actually 18. It still idles at 36kpa though. That means I've been tearing it up with 91 at about 23psi of boost! No wonder I had to pull all the timing out of it.

I put some fresh fuel in and bumped the timing a few degrees. So far so good. I'll report back when I get a new signal line ran to the MS.

Now, on the dyno, if I didn't hear a single bit of det on any of the pulls made but the dyno op says he could hear "something," who do I listen to? When I tuned the car on the stock b34 to 20 psi, I just went a couple degrees back from what was audible detonation on the street and left it there. No signs of scoring when it came apart for the rebuild.

[Scottinva]

Why don't you run higher octane fuel, 93 at least. Is it not available in your area? You can get 96 or more on some stations here. 93 is at every station?