Hemco Upper

[earlbrown]

That's where I remember the picture from years ago.  I wonder how a stock plenum would work with a hemco shaped plate under it.  Basicaly the same sized rectangle as the hemco under the plenum.  I have a feeling it would work like the hemco only with retaining some plenum volume(ish).


Thanks Steve. I remembered correctly. The Hemco is basically an elbow that dumps into the mental of the manifold.  Different direction that where I was going with my plenum design(s).

[ttipe]

The Radius Kid and I spent about 3 hrs talking with Red A. about "stuff". The Hemco came up in conversation. He basically drops the "F" bomb on the power plate. He uses the stock appearing hemco in his tse car. He was showing John and I around. There appeared to be no spacer.Red's car went 9.17 @ 148. An interesting tidbit, on cyls 1 thru 4 1.65 rockers, cyls 5 & 6 1.6. Several others are running a Hemco as well. Some have external engine management (XFI for example) or use XFI to alter their calibration. Red's guys use XFI to alter a file and then load the VE and spark tables in a chip. Dave Poppe is one of those. He goes nines. My goal is to run well on pump gas??? I have ported GN1's and a new engine on the stand.     

[Steve Wood]

I remember when Bamford went low nines with a PP.  I am getting old and don't remember if he was running a PTE upper or what, tho

I remember reading this long ago   http://www.hemcomachine.com/articles/article3.htm

too bad that we never see much serious science on Buicks.  Be interesting to see some flow bench results.  I would like to see both wet and dry flows given that so many of us spray alky into the up pipe

[Steve Wood]

That's where I remember the picture from years ago.  I wonder how a stock plenum would work with a hemco shaped plate under it.  Basicaly the same sized rectangle as the hemco under the plenum.  I have a feeling it would work like the hemco only with retaining some plenum volume(ish).


Thanks Steve. I remembered correctly. The Hemco is basically an elbow that dumps into the mental of the manifold.  Different direction that where I was going with my plenum design(s).

I think you would get a lot of disruption and distortion of the flow due to the edge affect of the plate.  Maybe a cast insert into the upper would provide better direction?

[ttipe]

Steve how much do I owe you for the Hemco and shipping? I'm hoping to make a flow core from the casting and see if our suspicions are confirmed. Talking about airflow (fluid dynamics) on a board is tough.Please observe that most of the hemco users that I know of (except the Tinman) are using external engine management (xfi,bs3 etc) systems which are controlling 6 one cylinder VE and Spark tables with about a 20% positive tolerance. The gain is the back pressure reduction across the compressor hot side. In my case I have ported Champ GN1's (better plug placement in chamber for faster burn; less octane req'd; relocated larger valves for "unshrouding" and the illustrious additional heat loss through the aluminum) along with a TA61 that "radius" worked like extrude hone for both compressor and turbine (about 10% volume flow increase-it screams like an F1 turbo when asked), PTE slic with improved scoop which helps to utilize the core surface area and xfi. Other stuff is part of this but I don't have the additional time at present. The goal is an 11 sec reliable pump gas (93 octane) T Type. The backpressure reduction across the compressor gradient will get me closer to the efficiency island of a 60-1 compressor wheel.   

[Steve Wood]

it's on the house...I never sell parts

[Steve Wood]

and, it's a 65mm

[ttipe]

Hey Steve thanks again so much for your generosity. If you have any further info, data or opinions please send them your input is valued. There is a lot of conflicting data/opinions from varying sources which is to be expected. The goal is back pressure /boost reduction and reduced knock tendencies. People celebrate running large boost numbers or lots of back pressure??? I may be able to bring some FEA tools into this. You will be the first to know about what we're doing and what we find out. When Radius and I went on this year's road trip we agreed to attempt a science based inquiry into the problem and any possible fix.

Thanks Again
Wayne Sherman

[Steve Wood]

Sounds like you are trying to go the right direction.  Technically, you are way of ahead of me these days because I have not been paying much attention.

If I were trying to do this, I would do anything I could to the heads to promote a consistent flame front and to help offset the thermal inefficiencies of the heads, I would think about some thermal coatings to retain heat in the chamber in a controlled manner as well as in the ports.  Also on the inside of the pistons...mayb e a dispersant.  Anything to even out hot spots.

I would look at over driving a high volume water pump to increase pressure in the block to try to alleviate any potential steam points.

I would look at compression in the 9.5-1 range to go away with a longer duration cam to keep the dynamic cylinder pressures down at lower rpms.

I would try to figure out the sweet spot of the ported turbo with regard to efficiency in order to push the most molecules possible into the cylinder and I would start with a low timing in the 16 deg range and not be surprised if optimum timing was no more than 18 degs.

I would also try to keep a narrow rpm band to simplify both fueling and timing and consider trying to use four gears instead of three in order to be able to keep the rpm band narrow to avoid having to twist the engine too hard as well as take some load off the turbo's air flow.

It's going to be all about controlling combustion chamber heat all the way to the turbo.  Might be time to look at downpipe design to try to avoid some of the backpressure problems by allowing very rapid expansion to cool the temp on the outlet side.

biggest air filter you can stick on the front of the turbo and a means of getting cool air to it...

Maybe a looser than normally required converter to get the turbo going without having to drive it by loading the engine to get enuf heat to get it going at lower rpm to give you more margin on the rest of the run so you could tune for top end without being penalized by the launch-heatwise

[deathraider6996]

I'm sorry Steve I've been readin this post and can't come to a conclusion on what your opinion is on the rjc pp in regards to a stock plenum. So would you recommend the pp with a stock plenum?

[Steve Wood]

yes...without hesitation.  However, unless you are tuning close to the edge for maximum performance, you may never know it's there

[deathraider6996]

Thanks Steve

[Steve Wood]

In this thread, we were discussing a scenario where the PP may impede the amount of air required to run down in the nines and/or a special case where he is trying to run elevens on straight pump gas with no alky, etc.

I am not sure the PP will interfere with that goal but this is an abnormal situation where it is desired to absolutely maximize all parameters so every possibility is being explored.  Consider it to be a science project

[deathraider6996]

Very helpful information. Thanks for the insight.

[ttipe]

Steve just a couple of observations. It looks possible that folks could have been using a Hemco with a lower intake egr chimney whether functional or not. This may cause poor air flow to the front cylinders ,uneven egr distribution or both where egr was not disabled mechanically and in the software. If things can look ok on pump gas (depending on consistent octane) things may look better on race gas.