BMW Turbo F1 Engine

The Renault on that page also has 7.5/7.0:1. There is obviously a performance reason to have a lower compression ratio. If I remember from the Offenhauser book I read, when they were dabbling in turbos, some had high 6.X:1 ratios and running stupid high boost.

There is also information on the Honda F1 engines on that page that claims they are 9.4:1.
HONDA V6 TURBO

Clearly, this doesn't apply to street applications, nor does it apply to maxing out (comparatively) small turbos. What's the best? I guess it really all depends. It's possible that not only is their turbo maxed out, but their engine as well. I can't claim to know, but I'm glad there are people out there experimenting still!

Rob10_99 said:

So I have always ran a stock 6-bolt bottom end. 7.8-1 compression.
My recent engine builds with the honda crowd, which range anywhere from 8.8-13.7-1 have made me wonder why the DSM crowd doesn't usually up the compression more than 8.5-1 or even 9-1?
A friend I work with is dead set on building turbo hondas with 10-1 compression.
I have heard/read in the past that anything over 10-1 is not suitable for boosting, such as 10.5+.
His B20vtec 35r powered SI hits 20psi at around 4400rpm.(520whp on c16, theres more but it was a quickie tune).
Back to the point.
What has kept us DSM'ers from using 10-1 pistons?
I have been on this board for YEARS. And read probably every post thats on this site.
I had always believed that 8-1 pistons and more boost/timing was the answer,
Now I think I have changed my mind on that issue, even up to 10-1 and 20psi seems to be the fastest to me.
(this goes along with WHY 500whp is achievable on a 4g63)
I for some reason think us DSM'ers have been pushed into buying 8.5-1 pistons for soo long,
The whole "turn up the boost" theory is good, but not the most powerful.
Anyone else think the same?
/rant

Click to expand...

I know several people with 10+ compression, including Myself, and I will be tuned on pump (still putting the engine together) I dont think that having high compression is as uncommon as it used to be....

Rob10_99 said:

So I have always ran a stock 6-bolt bottom end. 7.8-1 compression.
My recent engine builds with the honda crowd, which range anywhere from 8.8-13.7-1 have made me wonder why the DSM crowd doesn't usually up the compression more than 8.5-1 or even 9-1?
A friend I work with is dead set on building turbo hondas with 10-1 compression.
I have heard/read in the past that anything over 10-1 is not suitable for boosting, such as 10.5+.
His B20vtec 35r powered SI hits 20psi at around 4400rpm.(520whp on c16, theres more but it was a quickie tune).
Back to the point.
What has kept us DSM'ers from using 10-1 pistons?
I have been on this board for YEARS. And read probably every post thats on this site.
I had always believed that 8-1 pistons and more boost/timing was the answer,
Now I think I have changed my mind on that issue, even up to 10-1 and 20psi seems to be the fastest to me.
(this goes along with WHY 500whp is achievable on a 4g63)
I for some reason think us DSM'ers have been pushed into buying 8.5-1 pistons for soo long,
The whole "turn up the boost" theory is good, but not the most powerful.
Anyone else think the same?
/rant

Click to expand...

Your build/ your setup your goals all play a large factor in what compression ratio would
be best for your motor.

Ive read from a few reliable sources that on an average setup the compression increase generally gives about only 4% more power. I dont know all the variables though, and that could be more pronounced the higher up in compression you go.

In my unproffessional opinion, I think pump gas would look good around 8.5:1 to 9.1:1
compression with the typical 50trim tune etc.
With e85 or strict race gas, or methonal vehicle, 9.5:1 to 10.1:1 would be ideal.
I dont know if theres any gain in going beyond 10.1 if trying to run a lot of boost.
That would be a lot of stress with tuning, and most people should have some leeway in their setups. Its like with running too much timing advance, theres probably a piont of demishing gains.

Im positive it would be pointless to sacrifice a lot of boost for a little bit of compression as Im sure boost typically always makes more power then timing and compression and leaner AFR;s, but something ive always wondered is what gives larger power increases when added with that high boost- higher compression, or higher timing advance...?

Whenever i have to rebuild my stock 6bolt im going 9.1:1 compression forged pistons btw.

Black95awd said:

I know several people with 10+ compression, including Myself, and I will be tuned on pump (still putting the engine together) I dont think that having high compression is as uncommon as it used to be....

Click to expand...

Since im sure no one likes to lower their boost for this type of stuff,
on pump gas how much timing advance does this cause you to sacrifice for a knock free tune?
Do you have to take out timing timing vs your old compression ratio?

Black_Bullet said:

Since im sure no one likes to lower their boost for this type of stuff,
on pump gas how much timing advance does this cause you to sacrifice for a knock free tune?
Do you have to take out timing timing vs your old compression ratio?

Click to expand...

engine is not in the car yet therefore it has not been tuned so I dont have any answers for you. and I am by no means a tuner.

How much do u charge to tune a car?

Black_Bullet said:

Its like with running too much timing advance, theres probably a piont of demishing gains.

Click to expand...

Compression isn't really the true source of any "diminishment".
The limiting factor (point of diminishing return) is almost always a characteristic of the fuel used and its spontaneous ignition point.

The general concept of tuning an engine is to create the maximum cylinder pressure possible with the available contents of the cylinder right when the piston passes TDC, too much pressure/heat (can be from either too high boost, timing or compression) before TDC and you'll get knock.

The optimal timing advance depends on how quickly the fuel burns (builds pressure) compared to how fast the piston is traveling towards TDC. With a more dense charge (pre-ignition pressure) the burn gets quicker. The window of optimal timing and safe timing both decrease (in degree range and in degree value) the higher the cylinder pressure gets before ignition at a set rpm. That doesn't mean you lose power though.

Black_Bullet said:

Im positive it would be pointless to sacrifice a lot of boost for a little bit of compression as Im sure boost typically always makes more power then timing and compression and leaner AFR;s, but something ive always wondered is what gives larger power increases when added with that high boost- higher compression, or higher timing advance...?

Whenever i have to rebuild my stock 6bolt im going 9.1:1 compression forged pistons btw.

Since im sure no one likes to lower their boost for this type of stuff,
on pump gas how much timing advance does this cause you to sacrifice for a knock free tune?
Do you have to take out timing timing vs your old compression ratio?

Click to expand...

It's not always about how much. It's really more about how well everything works together and how well matched the variables are for each other. Higher compression does the same thing as more boost, it increases cylinder pressure at TDC.

. . . Yes, it's sinking in: 500whp and a 16g!!!

Just don't say it's because of the 16g. . . Possibilities are endless. Knowledge isn't.

tkelly27 said:

The Renault on that page also has 7.5/7.0:1.

. . .There is also information on the Honda F1 engines on that page that claims they are 9.4:1.

Click to expand...

What gasoline fuel variant are they running? Blends tend to be tuned for paticular tracks or even weather.Fuel specificgravity has a great effect on the results of ignition timing and burn rate. . .

The rest of the world does not have that luxury. We're stuck with burn rates of pumpgas or 101-110 race fuel. Water/meth injection can gain control. But what's the point if the fuel doesn't loose suspension before the flame front passes its proximity in the cylinder. READ: c16

delta448 said:

Compression isn't really the true source of any "diminishment".
The limiting factor (point of diminishing return) is almost always a characteristic of the fuel used and its spontaneous ignition point.

Click to expand...

It takes ALOT of effort to compress an aircharge to 10.5:1 vs. 8.5:1. That is a pumping loss. There is a point where that loss will not merit the increased work achieved by higher compression. It's all about timing from the kernal to the piston walls.

Thus what you say (which I feel is absolutey correct):

delta448 said:

The optimal timing advance depends on how quickly the fuel burns (builds pressure) compared to how fast the piston is traveling towards TDC. With a more dense charge (pre-ignition pressure) the burn gets quicker. The window of optimal timing and safe timing both decrease (in degree range and in degree value) the higher the cylinder pressure gets before ignition at a set rpm. That doesn't mean you lose power though.

It's not always about how much. It's really more about how well everything works together and how well matched the variables are for each other. Higher compression does the same thing as more boost, it increases cylinder pressure at TDC.

Click to expand...

More timing retard is neccesary for higher compression pistons. Why? The burn rate is increased. I'm not saying that timing has to be retarded because there is more knock. I'm discussing MBT (mean best timing). An ignition point where the most fuel is burned but not too much is burned before the piston can extract all the work.

So, with more compression, it is infact easier to find MBT. A low compression engine requires EARLIER MBT. But because of not churning the aircharge up enough, suffers from the gasoline falling out of supension back to droplets before the flame front can grow to the outer points in the combustion chamber. A high compression chamber yields a quick burn. Ignition timing can be later because MBT is later. No power is lost. No matter because, the fuel stays in suspension long enough to burn completely. Along the way to the piston walls, the kernal doesn't meet droplets which ignite and flash back. Enter: quick burn combustion chamber. . . A Honda hallmark.

1. Spark plugs in the center of the cylinder help this.
2. pintroof or "wedgeheads" help this. . . This is why hemi-guys lost to and loathed the 440 wedge heads!!!
3. tumble/swirl/piston shape helps this.
4. Etc.

I believe Marco prefers high compression. Pump gas or not. . .

GSX4BangR said:

How much do u charge to tune a car?

Click to expand...

Check out the website index

A plus to higher compression and lower boost is it might lower crank case pressure. Hence less oil leaks.

dsm-onster said:

It takes ALOT of effort to compress an aircharge to 10.5:1 vs. 8.5:1. That is a pumping loss. There is a point where that loss will not merit the increased work achieved by higher compression. It's all about timing from the kernal to the piston walls.

Click to expand...

Absolutely. I agree 100%, and I shouldn't have been so quick with my reply above. There are certainly some pumping losses associated with high compression ratios. At what point the trade off occurs, I honestly wouldn't know.

I feel that one of the many keys to the amazing success that Nate has had here with a 16G is Curt's selection of a CR that allows a good compromise between acceptable pumping loss and efficient use of the available air provided by such a comparatively small compressor (nonetheless provided while screaming along in the top righthand corner of its compressor map).

I believe it is possible to get more work out of the same cylinder charge with a higher CR than what is commonly used in the 4G63, even though the decay of pressure is greater in a high CR stroke-biased non-square engine design. Now combine that assumption with the amazing numbers we've seen him achieve on a stock block... =my best guess at how 500whp was achieved on the little 16G.

delta448 said:

Higher compression does the same thing as more boost, it increases cylinder pressure at TDC.

Click to expand...

It should be pointed out that higher compression does not significantly alter the flow charicteristics of the cold side like a higher boost pressure does so they can not be interchanged as far as power making goes.

Your theories sound like they have solid grounds though. I can't give a better guess... too much beer. Whatever happened to all the hoegarden pictures that come up on these threads?

tkelly27 said:

It should be pointed out that higher compression does not significantly alter the flow charicteristics of the cold side like a higher boost pressure does so they can not be interchanged as far as power making goes.

Click to expand...

Please explain further.

If you have an engine with 2:1 compression at 40psi boost and an engine with 10:1 compression at 8psi boost, which do you think makes more power? Which do you pick, compression by a factor of 5 or boost by a factor of 5? Tell me how flow plays into that? I realize right now you're probably thinking of how you're going to post a whole bunch of formulas using the numbers I provided. Please don't. Just give me a simple explanation, I want to understand what you're saying -not get into a pissing match.

tkelly27 said:

It should be pointed out that higher compression does not significantly alter the flow charicteristics of the cold side like a higher boost pressure does so they can not be interchanged as far as power making goes.

Click to expand...

??? Hmmm, what do you mean? Less boost is neccesary to make the same power if the compression is raised. And vice vesa. There's interchangability from that aspect.

So what I take from you guys posts, in terms of optimal increase of cylinder pressure (power)
its basically about finding an ideal balance between compression and timing, and MBT will be different
with different levels of airflow/ compression.
( i.e. what dsmonster stated about needing more retard w/ higher compression etc.)

I recall Evil Eagle only runs either 8.3 or 8.5 compression, I imagen at that level of air flow less timing and compression would be ideal. Was the compression ratio ever verified about Kurt browns car?
Id like to see back to back tests done at the same AFR regarding how compression and timing changes responds to different amounts airflow and how it can affect a 4g63s powerband and max power and etc and how they tie into each other...

Black_Bullet said:

Id like to see back to back tests done at the same AFR regarding how compression and timing changes responds to different amounts airflow and how it can affect a 4g63s powerband and max power and etc and how they tie into each other...

Click to expand...

Well, Curt Brown put down 460 on the same fuel with this same setup except for using a STOCK 1g 7-bolt (7.8:1). Vs. this run, we see a 40hp difference. This is a high compression motor with the same mods, unless TPG otherwize states. So just knowing the compression of this motor is all that's needed. In the other thread, Nathan mentions the e85 motor (the 'high compression motor') having about 2 compression points more. I'm sure they arn't going to tell you the compression. That's for the rest of us to play with and find out . . .

dsm-onster said:

Well, Curt Brown put down 460 on the same fuel with this same setup except for using a STOCK 1g 7-bolt (7.8:1). Vs. this run, we see a 40hp difference. This is a high compression motor with the same mods, unless TPG otherwize states. So just knowing the compression of this motor is all that's needed. In the other thread, Nathan mentions the e85 motor (the 'high compression motor') having about 2 compression points more. I'm sure they arn't going to tell you the compression. That's for the rest of us to play with and find out . . .

Click to expand...

You make some valid points, and at the level that this car is at, I dont doubt that 40whp is possible just from the increase in compression. I think I recall before Nate saying on the 460whp thread that timing went from like 17- 22 or 23 deg by redline. Was there anything mentioned about this timing map this run?
With what you mentioned about the 2 point increase, it should be reasonable to assume that the motor has 9.5:1 - 10.1 compression.

So with the dsmlink etc dsmers lining up to get their cars tuned from TPG - with the limitations of fuel and AFR changes, what are TPG going to be able to do differently to extract crazy power levels other than just finding peak hp for a given setup with dyno tuning...

I personally feel Kurt Browns car has something different about it allowing it to achieve what it has; and I dont think it has anything to do with any special tune in specific. I mean the tune is probably smack on, but they must've found some extremely efficient and podent combination of parts along with other tricks slipped in the melting pot.

Anywho, I guess higher compression should be the new way to go since dsmers shunned high compression for so long sticking to near stock levels. I guess people arent comfortable with tuning it on pump gas when thinking they'll have to keep their boost down. If i had e85 I wouldnt hesistate to run about 9.5:1 compression.

WOW! thank Heaven someone else sees what they are really saying here. . .

Black_Bullet said:

So with the dsmlink etc dsmers lining up to get their cars tuned from TPG - with the limitations of fuel and AFR changes, what are TPG going to be able to do differently to extract crazy power levels other than just finding peak hp for a given setup with dyno tuning...

Click to expand...

Nothing!!!! GEES! even Nathan himself said theirs nothing special about his tune on SEVERAL occasions!!! What the __ do these people think? The Finger of God is in your car, and we just have to crack the timing & a/f ratio code??? There's other stuff in that engine bay that's not in these guys cars who've posted, "You will be tuning my car. . ." I mean it's a laugh!!!! It's as if they think "HEY maybe F&F is right! I can tune on the fly in 10seconds and 50 upshifts! Just maybe, if I look at 3d maps long enough, some huge HPs will grow out of my head and into the engine."

TPG. . . Nathan in particular, are good, no GREAT tuners. But it's not a/f and timing they are tuning here. There's much more tuning aspects of which Curt Brown and TPG are taking control. You and I, with a little time could tune just the a/f and timing curves perfectly.

Black_Bullet said:

I personally feel Kurt Browns car has something different about it allowing it to achieve what it has; and I dont think it has anything to do with any special tune in specific. I mean the tune is probably smack on, but they must've found some extremely efficient and podent combination of parts along with other tricks slipped in the melting pot.

Click to expand...

YES!

Black_Bullet said:

Anywho, I guess higher compression should be the new way to go since dsmers shunned high compression for so long sticking to near stock levels. I guess people arent comfortable with tuning it on pump gas when thinking they'll have to keep their boost down. If i had e85 I wouldnt hesistate to run about 9.5:1 compression.

Click to expand...

Yea, someone kept blabbing about Shep runs this and Shep runs that compression. He also run's several TIMES 4 1000cc injectors with . . . What kind of fuel?

Curt posted his compression #'s as well as some info on the setup and tune on the DSMLink forums. Sorry I dont want to be the one to pull it from there and put it up here, so maybe he Curt or Nat will chime in and give up the info here. Still no logs though!!!

In all honesty, its no big secret or mystery parts. A bunch of people have said it already, parts that work really well together, light drivetrain, and an all around built car, not just a bunch of crap slapped together, he put thought into this build and extracted every bit out of the turbo he could. Obviously the car is tuned well. These guys can tune better than I can so thats all I have to say about that.

Great job, that car must be crazy fun to drive!!

PS. I'd like to see someone with a fully built car and a 35r or something put a 14b back on and see if they can come close!

ehh, the tuner uses nitrous in his 91gsx. id say he convinced the owner of the 16g to do the same. 499 horse 16g, internally gated? not buying it

Did you even read any of this? Where did you come from?

I would have to agree that its not just about the turbo and the tune. Light weight parts in the motor, freeing up horsepower probably do contribute. I would love to actually know the whole story, but for the most part this thread is becoming a lot of speculation now.

T9S1i said:

PS. I'd like to see someone with a fully built car and a 35r or something put a 14b back on and see if they can come close!

Click to expand...

That's what we're seeing here: Curt's car has the supporting mods to handle a 35R, but he has a 16G instead. How many other 16G cars have smim, big cams, big fmic, built motor, ect? There's no doubt those mods make power, we don't normally see that level of preparation on a typical 16g car.

pneumo said:

That's what we're seeing here: Curt's car has the supporting mods to handle a 35R, but he has a 16G instead. How many other 16G cars have smim, big cams, big fmic, built motor, ect? There's no doubt those mods make power, we don't normally see that level of preparation on a typical 16g car.

Click to expand...

X2, now if everyone else would just relize this.

Gsxy99 said:

that good for you?

Click to expand...

not really. Your logic is flawed and you are posting ignorantly (you admitted that yourself)

I can't wait to see some vids or at least some pics of this car and how it is set up.

bacalhau16 said:

I would love to actually know the whole story, but for the most part this thread is becoming a lot of speculation now.

Click to expand...

Purposefully, and tastefully done. After all, it wouldn't be nice to say "I'm not telling you why my 16g car is better than everyone elses."

We know what the boost & ambient temps at redline is (straight from Nate) for the 460whp stock block run. Thus, simply working like a speed density ecu, we know the engine airflow.

This makes me love a 16g even more! I've always wanted to get an evo 3 16g and I been plannin on fully building my motor so i'mma see how much ppower I can make outta mines now!