Audi A4R4 450HP CBEA (CR) Build

turbo johan said:

I'm using a 38 mm WG on my compound project.
But i thinking maybe it would be a bit small if the rest should go through the 40 mm exducer VNTturbine...
But i'll settle with a bit less hp

Stock pistons can handle a bit more than 200 bar PCP.
I think there are a lot of people driving around with high tq and spiking turbo which will give probleby on stock cr 250+ bar PCP....

Johan

Click to expand...

I have not done final selection on waste gate. We have talked about a TIAL unit.
@ Alex & Johan - your comments on PCP is exactly what I am mean. There are lower HP engines on this club that are probably exceeding the PCP that we will run. I am hoping this thread will help bring across a better understanding of these sorts of things to members. An engine properly designed and built can handle a lot more HP with less stress.

TDIsyncro said:

There are lower HP engines on this club that are probably exceeding the PCP that we will run. I am hoping this thread will help bring across a better understanding of these sorts of things to members. An engine properly designed and built can handle a lot more HP with less stress.

Click to expand...

I certainly understand what you guys have been saying on this topic, and for your sake I hope you are right. But would you care to elaborate on what parameters you will adjust to attain so much more power without dramatically increased PCP?

If we were to analyze this statement in terms of the cylinder pressure curve, you guys are hoping to "broaden" the curve, especially after TDC, of course, without driving up the peak pressure, thus delivering more work transfer from gas pressure to the piston.

There's really only three parameters that dominate the peak cylinder pressure vs. indicated power relation. Boost (charge flow), injection quantity, and perhaps most importantly, timing. Assuming enough fueling capacity to still inject the desired dose of fuel in a relatively short crank angle window, timing obviously has a huge effect. Too soon = high pressure without the broad curve to deliver power on the piston downstroke. Without changing timing, more air and fuel simply = higher pressure, without changing the location of peak pressure much.

So assuming optimal timing under maximum (safe) possible air flow and fuel quantity, what do you presume many ~200 HP TDI's are doing wrong now to have high PCP without the kind of power you are targeting? As I understand it many people around the 200 HP level are actually maxing out their usable injection duration range, thus delivering fuel from, say, 20 deg BTDC to some 15-20 deg after TDC. Wouldn't an extended injection and hence combustion event actually serve to lower the peak pressure? I guess I don't see what could be wrong with tuning in most of our high HP TDIs now, other than too advanced inj. timing, to cause high PCP without power to match it.

Using the CBEA platform and Common-rail, you have the option of programming multiple fuel injections/stroke. Without revealing any secrets, do you intend to prolong combustion after TDC through use of multiple injection events to attain a higher indicated power? How do you expect to mitigate exhaust gas temperatures if this is indeed your plan? Or do you expect combustion chamber / piston bowl shaping to play a large part in combustion propagation and PCP?

Enjoying the discussion.

Ok, I didn't really read all of the recent posts in this thread before I posted above.

Huge low end torque definitely could give super high PCP. Plus I just realized you guys are targeting peak power at 5500 rpm, so that helps.

shizzler said:

I certainly understand what you guys have been saying on this topic, and for your sake I hope you are right. But would you care to elaborate on what parameters you will adjust to attain so much more power without dramatically increased PCP?

If we were to analyze this statement in terms of the cylinder pressure curve, you guys are hoping to "broaden" the curve, especially after TDC, of course, without driving up the peak pressure, thus delivering more work transfer from gas pressure to the piston.

There's really only three parameters that dominate the peak cylinder pressure vs. indicated power relation. Boost (charge flow), injection quantity, and perhaps most importantly, timing. Assuming enough fueling capacity to still inject the desired dose of fuel in a relatively short crank angle window, timing obviously has a huge effect. Too soon = high pressure without the broad curve to deliver power on the piston downstroke. Without changing timing, more air and fuel simply = higher pressure, without changing the location of peak pressure much.

Click to expand...

There are some factors more fundamental to proposing any new method of combustion/heat release that you have missed.

Recall from Heywood that:
BMEP = IMEP_gross - TFMEP
I can get a high BMEP for a given gross IMEP because I can significantly reduce the PMEP (other parameters are largely unchanged). My simulations have shown that the turbo setup I have realized gives a very beneficial IMP/EMP ratio compared to other setups.

If we consider some of the builds that have been documented here, we are seeing torque values approaching 380 lb.ft. This equates to a BMEP of 34.4 bar, which is reached on largely stock bottom-end (i.e. stock compression ratios) 1.9 TDIs. My simulations suggest that on these builds the pumping alone contributes to over negative 3-4 bar MEP, and PCPs peak well north of 250 bar. I have shown PMEP in my "Insane..." thread to be very small and in fact positive in certain operating points. I can get IMP/EMP ratios of about 1.3, i.e., if my boost pressure is 4 bar (absolute), my EMP is in the order of 3.1 (absolute).

At the rated power point that would give 450 HP @ 5500 RPM, my BMEP is right around the 36.6 bar mark. But I'm reducing my compression ratio to a value anywhere between 15-16:1 compared to the builds that are keeping an unchanged CR from stock.

As long as I don't see any significant transient boost/EMP spikes, PCP will be the least of my concerns, but rather the heat flux that will be going through the pistons, cylinder heat and exhaust ports.

Using the CBEA platform and Common-rail, you have the option of programming multiple fuel injections/stroke. Without revealing any secrets, do you intend to prolong combustion after TDC through use of multiple injection events to attain a higher indicated power? How do you expect to mitigate exhaust gas temperatures if this is indeed your plan? Or do you expect combustion chamber / piston bowl shaping to play a large part in combustion propagation and PCP?

Click to expand...

The injection strategy at full-load, high-RPM operation -- regardless whether common-rail or not -- typically reverts to single injection. Multiple injections per cycle are not done as a rule at these operating points.

EGT is mitigated by a combination of maintaining a relatively lean equivalence ratio, effective charge cooling, low EMP, near-MBT injection timing and non-extended injection duration. An EGT plot is posted in the other-referenced thread. It is not expected that this engine will be subjected to sustained EGT levels exceeding 850°C, so short bursts into 900°C territory will not cause undue problems.

My little brain hurts

Thanks for the detailed reply, meister! I've got Heywood's book in front of me, and while his IMEP explanations are concise, they aren't all that detailed. But it's how I learned the concepts, for sure.

So a precise selection of manifolds, piping, turbos, and most importantly piston bowl (CR) are what you believe will keep PCP manageable. While I had obviously read and understood your intentions to lower the CR, it seems embarrassingly absent in my previous line of questioning. Wonder how the engine will cold start with 15.5:1 CR...

Do your simulations include consideration from the effect of load on FMEP? Piston and ring friction, bearing friction, etc, rises with load for a fixed engine speed. However this effect is probably lower than the reduction in PMEP you expect.

Those poor little pistons. They will be quite hot. Investigation into alternate / improved piston cooling nozzles might be wise.

Most current CR engines are 16.x:1 from the factory so 15:1 might not be that big of a problem.

The Toyota 2.2 D-4D D-CAT has a compression ratio of 15.8:1.

shizzler said:

Thanks for the detailed reply, meister! I've got Heywood's book in front of me, and while his IMEP explanations are concise, they aren't all that detailed. But it's how I learned the concepts, for sure.

Click to expand...

IMEP is pretty straight forward, actually. I know you know this, but for the others, it is simply the integral of the cylinder pressure trace over the entire cycle. Gross IMEP is the integral over 360 degrees crank angle from compression, combustion and expansion expressed as a mean pressure -- or stated another way -- normalized to a unit of swept displacement. Since the integral is over 360 degrees, gas exchange (PMEP) is not included. Net IMEP is the integral over 720 degrees, therefore includes PMEP. By definition, integrating a P-V diagram gives the exact same result as integrating the instantaneous moments acting on the crankthrows over the engine revolution. From this fact I can spot someone who doesn't know anything about engines when he talks about having more pressure in the mid-stroke of the expansion giving more torque, mainly because what you may gain in this part of the cycle you lose elsewhere... the whole cycle must be considered and not just one point.

So a precise selection of manifolds, piping, turbos, and most importantly piston bowl (CR) are what you believe will keep PCP manageable.

Click to expand...

Not only selection, but the layout and control of the turbos are fundamentally different, giving what I see as a much better IMP/EMP relationship over the entire operating range compared to other setups.

Do your simulations include consideration from the effect of load on FMEP?

Click to expand...

Yes.

Those poor little pistons. They will be quite hot. Investigation into alternate / improved piston cooling nozzles might be wise.

Click to expand...

I am specifying that the pistons be coated and that the under-piston squirters have an increased volume flow rate.

I think we all need to study up on our TLA's and ETLA's

TDIMeister said:

There are some factors more fundamental to proposing any new method of combustion/heat release that you have missed.

Recall from Heywood that:

BMEP = IMEP_gross - TFMEP

where TFMEP = total friction MEP = PMEP + RFMEP + AMEP
where RFMEP = rubbing friction MEP
and AMEP = accessory MEP

​

I can get a high BMEP for a given gross IMEP because I can significantly reduce the PMEP (other parameters are largely unchanged). My simulations have shown that the turbo setup I have realized gives a very beneficial IMP/EMP ratio compared to other setups.

If we consider some of the builds that have been documented here, we are seeing torque values approaching 380 lb.ft. This equates to a BMEP of 34.4 bar, which is reached on largely stock bottom-end (i.e. stock compression ratios) 1.9 TDIs. My simulations suggest that on these builds the pumping alone contributes to over negative 3-4 bar MEP, and PCPs peak well north of 250 bar. I have shown PMEP in my "Insane..." thread to be very small and in fact positive in certain operating points. I can get IMP/EMP ratios of about 1.3, i.e., if my boost pressure is 4 bar (absolute), my EMP is in the order of 3.1 (absolute).

At the rated power point that would give 450 HP @ 5500 RPM, my BMEP is right around the 36.6 bar mark. But I'm reducing my compression ratio to a value anywhere between 15-16:1 compared to the builds that are keeping an unchanged CR from stock.

As long as I don't see any significant transient boost/EMP spikes, PCP will be the least of my concerns, but rather the heat flux that will be going through the pistons, cylinder heat and exhaust ports.


The injection strategy at full-load, high-RPM operation -- regardless whether common-rail or not -- typically reverts to single injection. Multiple injections per cycle are not done as a rule at these operating points.

EGT is mitigated by a combination of maintaining a relatively lean equivalence ratio, effective charge cooling, low EMP, near-MBT injection timing and non-extended injection duration. An EGT plot is posted in the other-referenced thread. It is not expected that this engine will be subjected to sustained EGT levels exceeding 850°C, so short bursts into 900°C territory will not cause undue problems.

Click to expand...

I guess the last post of Dave must have been very important, i recieved 6! email notifications for it, instead of 1 *g*

TDIMeister said:

The Toyota 2.2 D-4D D-CAT has a compression ratio of 15.8:1.

Click to expand...

And it really sucks with cold starts.

I know as I have one...

Subaru are at 16.3:1 in boxer diesel and it starts fine.

oldpoopie said:

I think we all need to study up on our TLA's and ETLA's

Click to expand...

I'm lost with the acronyms. What do they stand for?

shadowmaker said:

And it really sucks with cold starts.

I know as I have one...

Click to expand...

I've had a Toyota Verso with that engine for an extended rental as well. The fuel consumption sucked too. It's just not a very good engine.

TDIMeister said:

I'm lost with the acronyms. What do they stand for?

I've had a Toyota Verso with that engine for an extended rental as well. The fuel consumption sucked too. It's just not a very good engine.

Click to expand...

TLA = Three Letter Acronyms
ETLA = Extended Three Letter Acronyms (usually four letters)

wich means you're not the only one lost with the acronyms

Haha, very true. A sticky post with a full list of commonly used acronyms might a good idea. We have such a high % of engineers on this site that our conversation gets (enjoyably) technical quite often.

Meister, good luck fully explaining IMEP in one concise paragraph! You did an admirable job, but you know that's just flying over some folks heads (understandably). Glad to hear you are improving piston cooling.

Alcaid said:

TLA = Three Letter Acronyms
ETLA = Extended Three Letter Acronyms (usually four letters)

wich means you're not the only one lost with the acronyms

Click to expand...

Touché. That's why I always try to spell out what uncommon acronyms mean. BMEP, PMEP and FMEP should be fundamental so they were not expounded upon.

Does this make things any easier?:


Didn't think so.

TDIMeister said:

The fuel consumption sucked too. It's just not a very good engine.

Click to expand...

I agree. It's just the perfect size car for the family right now.

TDIMeister said:

I'm lost with the acronyms. What do they stand for?
.

Click to expand...

Three Letter Acronyms and Extended Three Letter Acronyms.... LOL

Well, this thread made it all away back to page 6. lol Time for a project update.

Cams:
My cams are sitting at Colt Cams and he will be looking at the OEM grind and our options over the next two weeks. It has recently been brought to my attention that some of the lobes on the CBEA have actually spun causing engine damage. If you look back at the cam picks, you will see that they are hardened steel lobes on a tube steel core. We are considering some options for securing the lobes to the tube. In the end, I will be going to a custom billet cam set, but for now, we need to make the regrind work.

Head:
waiting for valve sizing, spring selection and max available lift numbers from Bill. IIRC, Bill may be able to continue on with comleting the porting in early April.

Rods:
Should Recieve these 1st week of March..these are a very nice billet units with a special spec to them.

Pistons:
need valve and cam feed back to spec fly cut size and depth. I am currently looking at some custom billet pistons that would incorporate some interesting design features. There would be no reinforced upper ring groove, so that is the one main negative trade off.

I have been making some slow progress on the girdle design. Just getting hole locations and some of the machining tolerance dims refined.

One of the steps was checking the bolt pattern with full scale paper template bolted to the block through the bolt holes for the mains, and pinning with the four corner oil pan bolt holes. The red circles indicate where additional holes are beng added to engage the BS rib holes and the two M9 holes at the rear of the block.

EDIT - the M9 holes I indicated are in fact M10x1.25, as TDIMeister points out.




One of the Chalanges with this design is to make it deep enough to clear the rods at BDC.

I am starting to look at options related to the piston coolers. Mainly how we will increase flow rate, and not have negative effects on the rest of the lubrication system. By running the drysump, I do have lots of oppurtunity for increase oil flow and pressure. It will also be easy to utilize a custom filter set-up, large reservoir, and custom oil cooler.

Any ideas on this guys? Any OEM piston coolers with more oil flow?


shot of the block showing the piston cooler locations



This is a pic of the piston cooler removed. It consists of a banjo style bolt, and a squarish block drilled for a tube. The tube has the end reduced in dia to create some oil velocity from the limited oil flow.




"A" Shows the small holes in the banjo bolt. Perhaps these shold be drilled to a larger dia
"B" Is the hole and tube inlet. There is not a lot that can be done here without replacing the tube
"C" Is the reduced tip. Could perhaps drill this out a bit larger.


There is also a small spring loaded ball at the tip of the banjo bolt. This would have some effect on oil flow through the cooler assmebly.

My guess is that there are two "A" holes in the Banjo bolt which won't pose much/any restriction to the "C" hole in the end of the tube. If there's only 1 then it should have a 2nd one.

I'm guessing that the check valve is there to prevent starving more critical parts of the engine if/when engine oil pressure is low. They probably crack at some relatively low pressure (10-20 psi?) to insure that cams/cranks/turbos get oil first before coolign the pistons.

If you want to increase oil flow through these I'd start by opening up hole "C". A small diameter change will make a significant flow rate change. Just insure you still maintain enough velocity to "shoot" the oil all the way to the bottom of the piston. This shouldn't be a problem, just something to keep in mind.

I'd suggest leaving the check and "A" hole(s) alone.

Do you have a target flow rate you're looking for?

not starting a P contest.

this whole build is just good old fashoned engine modifications, and for adding more than one piston cooler, drill holes on opposite side of crankcase and make up your own spray cooling nozzles, on outside rail tap into a good oil pressure source, like around oil filter or a galley.

with the amount of mods all ready, just go for more!

Ho-ly smokes. I can't believe that I never read this thread until now. What an awesome project. Tdimeister and I were on the same wavelength of keeping cylinder pressure under control years ago, and we've spoken about compound turbos before, but that was before he left for Germany and obviously he's gained a ton of experience (and access to proper simulation software) since then. I never imagined it would lead this far, though!

Piston cooling and oil cooling in general is going to be trouble, I can see it now. ronbros has the right idea. The stock piston squirters ain't gonna cut it, but they're not rocket science, either. I'd either keep them and drill the block to add more, or fabricate some replacement squirters that have larger flow passages. They're certainly not rocket science. You are GOING to need more oil flow - if only for cooling purposes. It might be worth investigating having a separate external oil pump running at a low pressure, whose only purpose is to send oil first through a dedicated radiator-type oil cooler and then straight to your new dedicated set of piston squirters. If you are using a dry-sump with a separate oil reservoir, the external oil pump shouldn't be a problem.

http://www.jegs.com/p/Moroso/Moroso-Door-Car-Dry-Sump-Oil-Pumps/1160110/10002/-1

ronbros said:

..........for adding more than one piston cooler, drill holes on opposite side of crankcase and make up your own spray cooling nozzles, on outside rail tap into a good oil pressure source, like around oil filter or a galley.

with the amount of mods all ready, just go for more!

Click to expand...

I like that idea.

Synchro - do the pistons have a cooling channel cast into them that the oil has to shoot into?

What might be the most simple is drilling/tapping into the existing oil rail and putting another OEM cooling jet in at the ~4:30 position to compliment the existing ones at the ~7:30 position for 8 total squirters

The check valve is there to prevent the squirters from dropping oil pressure at low RPM's, they also regulate maximum pressure at idle when cold. IIRC the earlier 4/5 cylinders valve opened at 25psi

I'm not too sure how much more cooling effect you would get by increasing the flow of oil to the squirter, at max flow I bet the bottom of the piston is flooded with oil, and if there is an oil channel in the piston it's likely that the channel will be full.

One cool thing to do if it's possible, since your running a dry sump is to pressureize the squirters with a seperate oil feed, from a cooler source than the mains and rods.

Thanks for the feed back guys.

Yes there is an oil channel in the OEM pistons.

Interesting ideas regarding adding a second oil cooler for each piston. With the OEM piston, that would add oil to the underside of piston but not the oil channel. Certainly that would be helpful but perhaps it would be nice to move more oil through the oil channel. I am not sure here. Open to opinions.
If I enlarge the existing oil squirter, Scott has an interesting point as well. Perhaps I can not even move more oil through the oil channel unless there is more pressure and velocity feeding the oil into the oil channels.
A third consideration is to add the extra oil squirter and drill an extra entry/exit hole in the bottom of the piston to create two entry and exit holes for the oil to move through. The billet pistons that I am looking at using have an external oil channel, not a cast internal channel and would respond well to a double squirter scenario.
The dry sump system that Issam is designing uses a number of scavanging stages and one pressure stage. It is an external mounted pump so there is the ability to split flow or regulate several flows at different pressures, even if a sepperate pressure stage has to be added. As for cooling the oil, it is open to do just about anything guys, so we can push for some decent temperature differential.

ronbros said:

drill holes on opposite side of crankcase and make up your own spray cooling nozzles, on outside rail tap into a good oil pressure source, like around oil filter or a galley.

Click to expand...

I re-read your post and I like the idea even more the second time. This would work great with the extra piston holes, and especially the billet pistons option.

Scott_DeWitt said:

One cool thing to do if it's possible, since your running a dry sump is to pressureize the squirters with a seperate oil feed, from a cooler source than the mains and rods.

Click to expand...

This would be my choice too. I think there's enough oil already.