CIS to ITB EFI conversion

[pampadori]

That Dyno chart shows gobs more area under the curve for the 911s cam. I know this only shows full throttle performance but I'd have a hard time giving up all that wot grunt! Are you claiming that the k45 cams make more torque at part throttle and that is what we can't see based on the Dyno chart?
I wonder if Mr. knight will weigh in.

[Tom_in_NH]

Dan,
Are you also running a lightened flywheel?

[scarceller]

Do you have full cam specs for both cams? The most single important cam event is 'Intake Close Event' (IC) you need to fully understand the importance of this event.

If a cam closes the intake valve later then it means that cam gives up a portion of the compression stroke and dynamic compression is reduced! You must understand this concept and it's consequences. This is why you can NOT decide your static compression ratio until a cam is chosen, pro builders build an engine around the specs of the cam.

So, I'm very interested to know when the intake valve closes for both these cams?

My notes have the 911s cam as these specs
Porsche 911S
Duration at 0.050" 267/235
Lift E/I .459"/.396"
LCA 97

This cam hits it's IC close point at about 50deg ABDC of compression stroke. It gives up 50deg of the compression stroke before compression can start.

This 50deg IC is very similar to that of a 964 cam and we know that using a 964 cam in a single plug engine needs about 10.5:1 compression.

[scarceller]

To help visualize the cam events this tool is super helpful! It really helps you understand the relationship of all 4 valve events. Intake open and close, exhaust open and close. The intake valve is not close at the start of compression stroke, it's still open for 50 deg of the compression stroke and that stroke only has 180 deg available.



Enjoy!

[scarceller]

I just read this that you wrote:

The lobe separation of the 911S cam is 98 degrees. The lobe separation of the K45 cam is 105 degrees. The valve duration and lift are very similar between the two cams.

So if the K45 LCA is 105 and the duration is about the same as the 911S it means you further delayed the Intake Close event by 12 more degrees! You now are giving up 62deg of compression stroke vs the 50deg with the 911s cam. The K45 cam needs more static compression to achieve the same dynamic compression with the 911s cam. This is likely why you are down on power with the K45 cam compared to the 911s cam.

Further complicating this discussion is that the 105LCA vs the 98LCA causes valve overlap to be reduced at TDC, if the LCA goes up and duration stays the same then overlap goes down. Reducing overlap helps idle quality and low RPM drivability. So I'm no surprised it idles better and takes off better at low RPMs with the K45 cam since it has more LCA.

The missing piece here is what the static compression ratio of this motor? That K45 cam likely needs 10.5:1 to 10.8:1 compression for very best results

Best book ever written on cams, octane and compression ratio is this book!
https://www.amazon.com/Tuning-Engine-Definitive-Performance-Economy/dp/1859606202

Enjoy.

[scarceller]

You can get this nifty free excel sheet here
https://www.tomei-p.co.jp/tool/valve_timing_graph_e.xls
Just enter the cam specs of your choice.
I create multiple tabs from the default tab, that way I can see each cam in it's own tab. Just play with LCA number and you'll see what that does to cam events.

[dannichols1474]

Photos of the Race Factory's fabrication work connecting the Knight headers to my existing Bursch sport muffler:

[eastbay]

Originally Posted by dannichols1474

Monday night after the dyno session, I got the Bursch 1.625" headers removed and installed the Knight 1.625" headers in preparation of getting the car towed to the fabrication shop on Wednesday. Turns out the fab shop needed to order material so we pushed the car tow until Monday.

Anyway, when I installed the Knight headers I saw that the #6 primary tube is in contact with the oil supply line directly beneath the oil cooler that sends oil from the oil tank to the oil pressure pump.



I didn't like the idea of the #6 primary exhaust tube heating, via conduction, the oil entering the engine even if that oil goes thru the cooler, if necessary, before it is distributed to the crankshaft bearings and the rest of the engine. So I applied insulating wrap to the oil supply line to reduce the exhaust tube heating.





Another thing I observed is the placement of the collector is very close to the exhaust valve covers such that I will need to remove the headers in order to perform a valve lash adjustment - this was not necessary with either the Bursch headers nor the SSI heat exchangers used previously.





Next up: Off to the fabrication shop to get the muffler connected to the Knight headers, then one more dyno session to see data comparing the Knight 1.625" headers to the Bursch 1.625" headers.

Not to be a Debbie Downer on this great thread, but that header contacting the oil cooler is a problem waiting to happen. You have options, but I would never run that setup as is.

[scarceller]

I have not mentioned this, but pushing 230 Wheel HP with a 2.8L engine is really amazing. Nice work so far.

[scarceller]

The ITBs you are using, can they be made longer in length? Can you get a longer horn to extend the length of the ITB? I ask because the overall length of the ITB helps dictate the peak torque sweet spot. Longer ITB length lowers the peak torque sweet spot.

[dannichols1474]

No, I mentioned 911S cam has combined LCA = 98 deg (96 & 100 - combined 98).

CR = 9.8 for this motor. I patterned after the 67-73 911S specs (Excellence Magazine) of 9.8-9.9.

[dannichols1474]

Originally Posted by eastbay

Not to be a Debbie Downer on this great thread, but that header contacting the oil cooler is a problem waiting to happen. You have options, but I would never run that setup as is.

So I talked with William Knight and thought hard of all of the various options for modifying the right side header to allow for 1/4 inch clearance under oil return line on the oil cooler.

Given that I had just gotten custom fab work completed to connect the Knight headers to my muffler, I did not want to make changes that would move the collector from its current location. So I started thinking about heating up the #6 primary tube and deforming it from a circle to an ellipse to get the clearance I was looking for.

I did a little math to look at the cross sectional area of the current tube compared to the cross sectional area of the flattened tube (approximated by an ellipse so I could easily do the math).

The OD of my header primary tubes are 1.625 inch with 1/16 inch (.0625 in) side walls, so the ID of the primary tubes is 1.50 inch. The radius is then 0.75 inch, and the cross sectional area is pi x r^2 = 1.767 inch^2.

If I deform the circle into an ellipse with a minor axis (a) of 0.625 inch and a major axis (b) of 0.875 inch (I am squishing the diameter from 1.50 in to 1.25 inch to get 0.25 inch clearance, so the radius goes from 0.75 inch to 0.625 inch in the vertical axis (minor) and 0.875 inch in the horizontal axis (major)), the cross sectional area is pi x a x b which is 1.717 inch^2.

So heating up and pounding down the #6 primary tube to get 1/4 inch clearance under the oil cooler will reduce to the cross sectional area of the deformed regions by 2.77% and dyno data from the Engine Masters show on TV has shown that there are negligible effects to torque and HP, so I decided that was the corrective action I was going to take.

I bought a 3 ft section of 1/8 inch thick, 3 inch aluminum angle stock and fabricated a fixture to hold the primary tube head flanges to prevent them from moving out of alignment with each other.



I had clearly marked on the #6 primary tube the two areas that needed to be worked on.



I worked on one section at a time. Using a MAP gas torch I heated up the area to be deformed, then laid a piece of thick wall gas pipe on the heated area and struck the gas pipe with a single jack sledge hammer. I repeated the heating and pounding process until I had achieved the desired amount of deformation. Then I repeated the process on the second section.



I let the header and fixture cool back down to room temperature, then removed the fixture and reinstalled the right side header and reconnected the headers to the muffler.

I left the insulating wrap on the oil return line and verified that I now had 1/4 inch clearance between the #6 primary tube and the oil return line.

[mikedsilva]

I'm sure you will be ok with this fix. Thanks again for such a detailed thread.

[scarceller]

The headers just needed to drop down another 3/8", so the down tubes should have been slightly longer but they do look well made.

[mb911]

Man I hope William made it right with you on that. I know those headers were not cheap and should fit better. I am glad you got it fixed to your satisfaction and you should be up and running

[dannichols1474]

I just got back from the dyno shop. Here are the test results of my rebuilt 2.8L engine with K45 cams and 1.625" Knight headers versus 1.625" Bursch headers.

Gary was able to tune out the 3500 rpm to 4000 rpm torque dip we had with the Bursch headers by adding fuel to the VE table and 1-1.5 degrees of advance to the ignition timing table with the Knight headers.

With the Knight headers, we were also able to recover half of the max wheel torque we lost going from the 911S cams to the K45 cams.

All that and I ended up with a car that is MUCH MORE enjoyable to drive than when I was running with the 911S cams.



Now, if you are like me and having a hard time keeping all these dyno results straight in your head, see the following summary table:



Enjoy.

[dannichols1474]

For a recap, here are the previous dyno results:

Stock 2.7 engine without smog, ITB EFI next to CIS



2.8 engine with 911S cam / 1.750" Bursch headers vs stock 2.7 w/o smog and ITB EFI



2.8 engine w/ 911S cam / 1.750" Bursch headers vs 2.8 engine w/ 911S cam / 1.625" Bursch headers vs Stock 2.7 engine w/ ITB EFI



2.8 engine w/ 911S cam / 1.625" Bursch headers vs 2.8 engine w/ K45 cam / 1.625" Bursch headers



2.8 engine w/ K45 cam / 1.625" Bursch headers vs 2.8 engine w/ K45 cam / 1.625" Knight headers



Dyno results summary table



Enjoy

[KNIGHTRACE]

Excellent Work great data for the community. William

[Tom_in_NH]

The area under the curve (average power) looks much better with Williams headers/cams combo!

Very grateful that you have taken the time to carefully share all your testing with us!

[al lkosmal]

Dan,
Nice summary of your results. As i followed your posts, I appreciated the blend of data and personal driving results/comments, illustrating that the highest dyno numbers do not always translate into the best driving experience......congrats to for going down this particular slippery slope.

regards,
al