S38B35, cams and compression tuning

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robertodonnell
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Location: NSW

S38B35, cams and compression tuning

Post by robertodonnell »

Hi all,

I have the intention of swapping out the doughy cams for something that will make the engine more like its 286 HP brother,. I am considering what to get, but essentially I am happy to have a slightly angrier idle than an S38B36, but not a silly choppy idle, if I can increase the mid range torque and top end HP. I have UK RHD headers and a new performance exhaust to go with this too. I would like to know what cams you guys would suggest?

Now... relating to comp ratio...if I was to go with a similar or a bit more aggressive cam to the b36, would an increase in compression be necessary, or yield an improvement in power? The difference between the 2 engines is negligible on paper (9.8 vs 10 to 1), and I would like to use 95 or 98 RON fuel with no problems.

Cheers,

Rob
Randomg
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Re: S38B35, cams and compression tuning

Post by Randomg »

What I have at the recommendation of what was one of the top s38 builders at the time (not sure where Paul Burke went though, retired maybe) is the b36 cam on the intake. The b36 cam on the exhaust also makes a difference, but Paul told me it wasn't worth the money and to just use the stock one. I got the feeling from talking to him and his partner that going with much more lift or duration is not worth the loss of low end torque for a street sedan.

His recommended build was his 10.5 pistons, a b36 cam, an 86mm crank and a certain cam timing he had me set after slotting my cam sprockets. I don't know if part of getting it all to work the way it does has to do with his piston design. At one point he said getting the quench right was part of it, which you might not get with any old high performance piston. Then lastly you have to up the fuel rate, which is either with a new chip or a modified FPR. For me it's been good for between 290-300 whp. I know I've seen 11.0 compression get close to 310 on this forum.
robertodonnell
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Re: S38B35, cams and compression tuning

Post by robertodonnell »

300 whp would be nice if it isn't too cranky down low. I have a new tuneable ecu to use, so fuel and timing is sorted there.

One thing I've heard is an m30b35 rotating assy fitted into the S38 block, with pistons machined to zero deck. I have to call this guy to hear what the specific details are, but he told me closer to 400 than 300 whp!
Randomg
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Re: S38B35, cams and compression tuning

Post by Randomg »

No way you're getting over 350whp without sacrificing a lot of low end torque or adding a lot more displacement. Engine builders overstate what you're going to get. I was sold that I'd get 310whp if I followed a certain build, I got a little under 300, and had to spend an extra $2k to get there...
slownrusty
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Re: S38B35, cams and compression tuning

Post by slownrusty »

@Randomg - What are your mods?
41magfan
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Re: S38B35, cams and compression tuning

Post by 41magfan »

Run M88 headers, e34 M5 B36 cams and the cam sprockets applicable with the cams. You ge the M88 headers and the M88 cam profile along with correct cam timing
robertodonnell
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Location: NSW

Re: S38B35, cams and compression tuning

Post by robertodonnell »

Do you have any dyno results of the change?
Galahad
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Re: S38B35, cams and compression tuning

Post by Galahad »

robertodonnell wrote: May 10, 2022 10:33 PM ...I have to call this guy to hear what the specific details are, but he told me closer to 400 than 300 whp!
I don't have specific input on S38 engine mods, just pointing out that getting over 100hp/l isn't going to happen NA without building a straight race engine and revving it well past 7k, which is definitely not what you want in a street car.
M5BB
Posts: 1560
Joined: Jun 13, 2007 10:13 AM
Location: Peachtree Corners, Georgia

Re: S38B35, cams and compression tuning

Post by M5BB »

Hey Rob,

I don't come on here much anymore.
I still have my BB M5 though.

I did a impressive build starting in 2009 and an additional tweak in 2015.
Couldn't fine all the write ups but here is the main one.

viewtopic.php?f=5&t=81942&start=50

After the 2015 tweak I got 361 HP at the crank and 330 Tq.

It's a ball to drive and well know in my area and in the M5 groups.

I've always wanted to go to a modern Motronic set up and could get even more power.
The limit currently is no knock sensor.

Gary
euroclassicmotors
Posts: 69
Joined: Oct 23, 2009 11:39 PM
Location: California
Contact:

Re: S38B35, cams and compression tuning

Post by euroclassicmotors »

Galahad wrote: Jun 14, 2022 10:43 AM
robertodonnell wrote: May 10, 2022 10:33 PM ...I have to call this guy to hear what the specific details are, but he told me closer to 400 than 300 whp!
I don't have specific input on S38 engine mods, just pointing out that getting over 100hp/l isn't going to happen NA without building a straight race engine and revving it well past 7k, which is definitely not what you want in a street car.

Hi,

This is absolute false information you are posting.

Long time ago I decided to fact that one does not need a fully build
"straight race engine" as you called it in order to produce 100hp/per 1000cc.

One needs to understand that these engine are very de-tuned for the street
in order to stay adequate with the HP at that ERA !!!

The S38 B35 in the link makes 101hp per liter on stock internal.
https://www.youtube.com/watch?v=SPWFAoIsiOo&t=20s

The upgrades I made are only camshafts and exhaust system,
carbon/plastic intake is mostly to save 18pounds from the std intake
and solid tune.

Regards,
Anri
euroclassicmotors
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Re: S38B35, cams and compression tuning

Post by euroclassicmotors »

M5BB wrote: Jun 15, 2022 5:11 PM Hey Rob,

I don't come on here much anymore.
I still have my BB M5 though.

I did a impressive build starting in 2009 and an additional tweak in 2015.
Couldn't fine all the write ups but here is the main one.

viewtopic.php?f=5&t=81942&start=50

After the 2015 tweak I got 361 HP at the crank and 330 Tq.

It's a ball to drive and well know in my area and in the M5 groups.

I've always wanted to go to a modern Motronic set up and could get even more power.
The limit currently is no knock sensor.

Gary
Gary,

I have seen your car and your nice engine build. 11CR, ported head, M88 headers
3.6 cams. Your CP pistons are 94mm as far as I remember which is a common size
over the worn and old 93.4mm std bore. 84x94=3500cc 295rwhp. 93 Octane gas.
Keep in mind that DynoJet is 14.7% drive train loss not 17% as you consider and
calculate. 345hp crank -14.7% = 295rwhp.



Efficiently is the key:

I reached the absolute max of what a stock 3.535cc can produce on stock 10CR.
Stock 260k miles pistons, new rings, stock head ports, good valve job, guides etc.
Upgrades are: Cams, exhaust system.

I started with 300rwhp and was able to stretch the power up to 318rwhp on DynoJet
which is very consistent compared to other dynos which I am not fan of their
inconsistency... 370hp crank SAE -14.7% comes to 315rwhp and 254RWTQ

https://www.youtube.com/watch?v=y5S6tIOoNGU

Regards,
Anri
Last edited by euroclassicmotors on Jun 17, 2022 12:53 AM, edited 1 time in total.
robertodonnell
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Joined: Feb 17, 2019 6:27 AM
Location: NSW

Re: S38B35, cams and compression tuning

Post by robertodonnell »

Hi Anri,

The B35 build interests me a lot! I haven't the luxury of Euro headers, as I am right hand drive, so I have UK headers. I will also be keeping with the stock intake plenum, but using a newer ECU, so the old flapper air flow meter will be removed and this will increase air flow.

Can you tell me a bit about your cams and cam gears? Also, what was mid range torque like? Most of this car's use will be street, so I don't want to lose driveability for the sake of top end HP.

I would love to see what your HP/TQ curves look like, if it's possible to share?

Cheers,

Robert
Galahad
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Re: S38B35, cams and compression tuning

Post by Galahad »

euroclassicmotors wrote: Jun 16, 2022 1:19 PM ...
One needs to understand that these engine are very de-tuned for the street
in order to stay adequate with the HP at that ERA !!!

The S38 B35 in the link makes 101hp per liter on stock internal.
https://www.youtube.com/watch?v=SPWFAoIsiOo&t=20s
...
That's an impressive engine; I underestimated what you can do with them.
Why would BMW ship a de-tuned engine from the factory if you can get this much power without downsides?
euroclassicmotors
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Re: S38B35, cams and compression tuning

Post by euroclassicmotors »

Galahad wrote: Jun 16, 2022 10:07 PM That's an impressive engine; I underestimated what you can do with them.
Why would BMW ship a de-tuned engine from the factory if you can get this much power without downsides?
Galhad,

Thanks for your reply.

The cammed S38 in the red M6 is timed to be efficient from Idle
to around 7100rpm
Galahad wrote: Jun 16, 2022 10:07 PMWhy would BMW ship a de-tuned engine from the factory if you can get this much power without downsides?
Very simple answer to your question:

These are all restriction applied to a street engine.

-Emission regulation via mapping, exhaust design etc.
-Fuel economy has little to play but its on the table
-increasing HP from previous Generation S38 engine.
-Staying with the industry largest BMW competitor Mercedes.
List goes on and on..

If you think BMW did answer your question E28M5 Euro vs E28M5 US
version 256hp SAE vs 286hp or around 280SAE

Everybody looooves E28M5 M88/3 or M635CSi and its allwasy the desired
pick over the US E28M5 or S38-B35.

So, the Red M6 is faster than stock E46M3 by 6 cars I did runs from 20-140mph
and about 10cars on a stock M635CSi. The owner of the E46M3 accused me that
I have hidden Nytro-Shot. lol....

Another answer to your question. 1992 BMW made the first street M engine
which broke the barrier of 100hp per liter engine code S50-B30 286hp DiN.
The second Gen S50-B32 is also 100hp per liter.

3rd Gen inline-6, s54 is also 100hp per liter. But looks like you have
not asked yourself why E39M5 is only 80.4hp per liter ? This is what I meant
earlier when I said that these engines are de-tuned for the day they were in
production. Simple answer to your question. Its not that they could not make
the S62 5.0l with 500hp DiN but then it was going to be 120hp more than the
Mercedes W210 E55 which is not what and how BMW do make power.

Then if the S62 was 100per liter at 500hp then how many HP the S85 should
have been ??? 550-600hp ? then F10 M5 should have been 700hp...

See, engines for street is very different from what "One can do" because there
are many rules and requirement to meet.

The Red M6 is so much fun to drive the early torque make the car drive light.
It's dialed to be all street friendly.

The link here is stock 3.8 bottom, head itb etc https://www.youtube.com/watch?v=IFsFkgYn0EE
Same principle 104hp per liter with bolt-on cams, exhaust, air box. it makes 395hp-SAE.
no down side form drive-ability. if you can live with little bit lumpier idle then you are
fine. This E34M5 Euro is faster than E39M5.

Regards,
Anri
M5BB
Posts: 1560
Joined: Jun 13, 2007 10:13 AM
Location: Peachtree Corners, Georgia

Re: S38B35, cams and compression tuning

Post by M5BB »

euroclassicmotors wrote: Jun 16, 2022 1:57 PM
M5BB wrote: Jun 15, 2022 5:11 PM Hey Rob,

I don't come on here much anymore.
I still have my BB M5 though.

I did a impressive build starting in 2009 and an additional tweak in 2015.
Couldn't fine all the write ups but here is the main one.

viewtopic.php?f=5&t=81942&start=50

After the 2015 tweak I got 361 HP at the crank and 330 Tq.

It's a ball to drive and well know in my area and in the M5 groups.

I've always wanted to go to a modern Motronic set up and could get even more power.
The limit currently is no knock sensor.

Gary
Gary,

I have seen your car and your nice engine build. 11CR, ported head, M88 headers
3.6 cams. Your CP pistons are 94mm as far as I remember which is a common size
over the worn and old 93.4mm std bore. 84x94=3500cc 295rwhp. 93 Octane gas.
Keep in mind that DynoJet is 14.7% drive train loss not 17% as you consider and
calculate. 345hp crank -14.7% = 295rwhp.



Efficiently is the key:

I reached the absolute max of what a stock 3.535cc can produce on stock 10CR.
Stock 260k miles pistons, new rings, stock head ports, good valve job, guides etc.
Upgrades are: Cams, exhaust system.

I started with 300rwhp and was able to stretch the power up to 318rwhp on DynoJet
which is very consistent compared to other dynos which I am not fan of their
inconsistency... 370hp crank SAE -14.7% comes to 315rwhp and 254RWTQ

https://www.youtube.com/watch?v=y5S6tIOoNGU

Regards,
Anri
I don't know where you get your numbers from?
The guy that owns the dyno is a very respected race team engineer and a graduate of Georgia Tech.
He uses 17% all the time with the race cars he tunes on his dyno. Not a rented dyno.
So I'll stick with the numbers I use along with many others that have been on his dyno.
Mines not a stroker motor, just a motor built to follow the M88 design with a little more compression.
I live where we have 93 octane gas, CA does not.
BTW this same engineer designed a NA 450 HP S38 motor in 2002 long before any of us.
euroclassicmotors
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Re: S38B35, cams and compression tuning

Post by euroclassicmotors »

M5BB wrote: Jun 15, 2022 5:11 PM I don't know where you get your numbers from?
The guy that owns the dyno is a very respected race team engineer and a graduate of Georgia Tech.
He uses 17% all the time with the race cars he tunes on his dyno. Not a rented dyno.
So I'll stick with the numbers I use along with many others that have been on his dyno.
Mines not a stroker motor, just a motor built to follow the M88 design with a little more compression.
I live where we have 93 octane gas, CA does not.
BTW this same engineer designed a NA 450 HP S38 motor in 2002 long before any of us.

Hi Gary,

I can tell you and the tuner have not done the proper test otherwise you wouldn't be calculating 17% drive train loss.
The 17% a number came from SAE (Society of Automotive Engineering) they came with number for RWD cars but
that does not mean that this is applied on Dyno-Jet.
M5BB wrote: Jun 15, 2022 5:11 PM I don't know where you get your numbers from?
Very easy. Factory BMW Motorsport GmbH AG don't lie on the power they are selling us all
of their cars which roll out from Munich. European industrial standard is measured via
DiN. In US rates the power in SAE.

Long ago before I started making improvements on S54 S38 S14 S62 etc. I took bone stock
cars to the same Dyno-Jet I work with and have done a test to determine the real loses. I
have done 7) E46M3s in a stock form before performance parts are installed.

Bone Stock E46M3s make on Dyno-Jet +/-285RWHP SAE correction.
BMW AG E46M3 power is rated at 333hp SAE at the crank.

The equation/formula is as follow: 333hp (crank) -48hp=285rwhp you take the 48hp divide by 333=0.144x100=14.4%
The 14.4% is how the proper mathematical equation is done. Again, Its black and white 333hp crank 285rwhp=14.4%.

If we take your equation of 17% the stock E46M3 at 285rwhp will be at 345hp crank SAE. 60 divide by 345crank
=285rwhp which equals to 17% drive train loss which proves the 17% is inflated number. E46M3 never entered US
at 345HP crank SAE.

Here is what a bone stock and 1 owner customer of mine E39M5 makes after proper maintenance
https://www.youtube.com/watch?v=7z1hdTtCLl4

395(SAE) hp-339rwhp=56 56-395=14.1% Dyno-Jet drive train loss.

https://www.youtube.com/watch?v=d8Id70R77oo Bone stock E34M5 first run was 265rwhp with the OEM
Eprom 310-265=45-310=14.5% drive train loss.

While the car was sitting on the dyno I Pulled the ECU and changed the chip back on the runs and it made gains
of 10rwhp at 276rwhp. 323-76=276rwhp. 47-323crank=14.5% drive train loss.

https://www.youtube.com/watch?v=e7nLYTqrtg8&t=3s my bone stock engine with cams and exhaust system
and custom Eprom chip made 309rwhp Dyno-Jet. Same engine with custom management made 315rwhp Dyno-Jet
on cams exhaust system and tune.

All the tests were/are done on California pump 91 Octane fuel.

I know you are on 84mm stroke.

Regards,
Anri
Randomg
Posts: 463
Joined: Jul 12, 2007 3:12 PM
Location: Seattle

Re: S38B35, cams and compression tuning

Post by Randomg »

Lots of assumptions above...

Not all engines make the same hp from the factory. It's not that they are lying, it's that they have to pick a number because manufacturers don't give ranges.

Dynojets are not all the same, there's some variance between setups. You talk to various dyno operators and they will often tell you there's reads low or high based on what customers have told them.

The goal should be to compare readings before and after mods on the same dyno or to compare different cars on the same dyno, unless you're just trying to do a digital drag race vs other cars based on what the factory rated them. The most useful number in my opinion for people on here looking on what mods to do is what was your before and after.

I had 235 whp on a dynojet with 140k miles and a JC chip. I had 294 on what I think is the same dynojet (it was many years later) with 94mm 10.5 pistons, b36 intake cam, custom valve timing, 86mm e34 m30 crank (lighter than the early ones I'm told), euro headers, miller maf, and war chip. I was hoping for 310 based on what engine builder told me without euro headers or maf. Never got there with the valve timing he gave me for max torque (as opposed to max hp).

14.5 != 17 tells me dynojets read high, which is what most people will tell you anyway.

I guess people just like to quote the biggest number on the internet.

Why didn't s38s or m88s make this much stock? Because of gas variance (and I suspect it was even worse in the 80s) and emissions. I don't think anything was sold with 11.0 CR in the 80s.
///M
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Re: S38B35, cams and compression tuning

Post by ///M »

Neanderthal man probably had the same arguments. With regard to manufacturers being honest you just have to look at recent events with emissions and fuel economy. They are being taken to court over the issue. They cheat and always have done with numbers. In fuel economy tests they use tape to streamline gaps and turn mirrors in and anything they can do to fit within the test procedure.
When Jaguar achieved 150mph with an etype they used a specially prepared cars, they were prepared by the works team. They were not of a production line car. How many could achieve 150mph? Unknown. You would have to test them all. You would then have a mean or average top speed which would be lower, not such a headline.
If you are selling a product or service then of course you give the biggest number. The problem is when people believe the hype.
So when BMW or others quote a power output what are the quoting. Are they quoting peak power output achieved by their motorsport division.

I was just looking at an old magazine where an s50 b32 engine was claimed to have 350bhp with a Superchips performance chip, a performance exhaust and air filter. So a claimed increase of 30bhp almost 10% improvement. If you are selling something the truth is not important it is what people believe to be true.
robertodonnell
Posts: 49
Joined: Feb 17, 2019 6:27 AM
Location: NSW

Re: S38B35, cams and compression tuning

Post by robertodonnell »

And, in my case I am looking for no real HP number, just what can be achieved with the use of a custom ECU and the correct cam timing. I have never looked for bragging rights with a dyno, but using it to create a before and after situation, well, that will be an interesting comparison!

It is interesting to see how de tuned and how much potential these engines have. Coming from a Small Block Mopar background, I can tell you that some milled heads, a good cam and some 10 to 1 pistons is enough to wake up a sleepy 318. A lot! Pity these S38s aren't as economical to do the same with.
///M
Posts: 60
Joined: Apr 17, 2009 11:21 PM

Re: S38B35, cams and compression tuning

Post by ///M »

Hi robertodonnell
Your mention of the RHD exhaust manifold reminded me of when I got my M5 RHD. From reading about the cars from new they appealed to me. I was surprised by the manifold as I thought it would have a similar manifold to the Euro model. It was rated at 286bhp and I had never read about the RHD version having less bhp. Unlikely producing the same power output with a worse manifold design or was the manifold of the Euro version no benefit?

http://www.catcams.com/products/camshaf ... ge=english
Ifyou have super unleaded 98 Ron then a higher compression ratio would be helpful.
Parts for these engines are expensive and you should check availability of the likes of chain guides which when I bought some there were limited amounts left. May have been reproduced now.
robertodonnell
Posts: 49
Joined: Feb 17, 2019 6:27 AM
Location: NSW

Re: S38B35, cams and compression tuning

Post by robertodonnell »

Yes we have 98 Ron in Oz, but I'm leaning towards not upping the comp. I don't want to sink money in too deep, so the cam gear change and proper ECU may be it for the meantime. The guides are a musth though, I've been told to expect to find them in disintegrating the sump.

Rob.
///M
Posts: 60
Joined: Apr 17, 2009 11:21 PM

Re: S38B35, cams and compression tuning

Post by ///M »

If BMW engine parts are expensive then the M parts are a few levels above. BMW have a pricing policy on older cars that as the part supply diminish the price goes up and up. I bought one part for €69 which is now €270.
The issue with the chain guides is as you say the material wears away. Normal wear should see twin chain tracks on the pads. If it is like that and not worn to deep I have sanded the surface smooth. The thickness of the material and how it responds to being resurfaced is important. Ideal world replace all the guides. The broken up chain guide is more the plastic guide which is similar to the M30 plastic guide. Using the hydraulic tensioner from the s50b32 can increase the tension on the chain. They are available aftermarket.
Looking at the price of the top guide €400 alone and if still available then if you open up the engine to rebuild then prepare for major bills. I remember when I got my M5 asking a garage in the UK that were Mpower specialists for a list of parts and labour they recommended for a chain replacement. In the 90's the cost was around £2000.
robertodonnell
Posts: 49
Joined: Feb 17, 2019 6:27 AM
Location: NSW

Re: S38B35, cams and compression tuning

Post by robertodonnell »

Let's hope that a previous owner has already taken that plunge then!
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