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Tests 4&5 are the results for my cylinders 6&5. Test 5 is cylinder 5 w 731 intake manifold. 1&2 are a stock 885 and AMC for comparison.
I'm not sure what a 731 should or could flow but we learned that my machinist did not back cut the valves or hog out the seats to benefit the +2 valves. John says this will make a big difference so I'm hunting for a machine shop to do that. There's also an 8cfm difference between the 2 cylinders which I will try to balance out.
At this stage we know it's better than the AMC and I'm thinking/hoping with the seats improved it should be comparable to an 885, but with the higher compression which was the point in using the 731 in the 1st place.
Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com
a stock 731 tops out at about 140 iirc. ill try find the sheets.
yeah you have to adjust the throat the suit the valve otherwise it is just represents a bigger blockage then adjust the transition of bowl and short side to suit the new seat area
the amount of air you can move at higher lift points will be dictated by the minimum cross section of the port probably somewhere near the guide on a 731 head. i cant find the silicone moulds and sections i did but its pretty tight around there. people worry about hogging ports but too little area is just as bad if you want to make power
I recall seeing your silicon molds. Based on our test this 731 maxed at 151 and 159 on cylinders 6&5 and should improve with a back cut and 70 angle below the seats. I could feel a difference in the turn on the short side between the 2 cylinders so Im hoping the flows will even out somewhat when I clean that up. FF didnt think 8 cfm at WOT was enough to worry about on a DD but I'll see what I can do.
I erred on the side of too little for obvious reasons (hard to put it back) and FF seemed to agree I didnt go over board.
We also found a difference in the b23 outer springs with the new b25 inners I bought VS a pair of stock b25 springs. Seems Im 10 lbs higher which shouldnt be enough to hurt anything. Again I have an IE 272 going in.
Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com
stock 731 entry size is 36 mm if you slice it at point of minimum CSA its 28.7 mm equivalent diameter before enlarging again back to the seat. Pipemax says it needs about 32.5 mm for a 2.7L targeting about 200-210 flywheel.
for reference a 885 starts off at about 37.5 mm and gets down to 34.5 mm at the same point (iirc) before enlarging to again
Your original PDF doesn't work on your site, and with the photobucket crap, I think I'm missing some bits. Mainly I'm curious on the 885 with eta intake. I'm looking for a midrange edge, and was thinking this might be an answer. You were saying a port matched eta manifold, bored to mate to an i intake, flows almost as well as an I intake? Longer runners usually help mid range too, right? Or am I way off here?
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Your original PDF doesn't work on your site, and with the photobucket crap, I think I'm missing some bits. Mainly I'm curious on the 885 with eta intake. I'm looking for a midrange edge, and was thinking this might be an answer. You were saying a port matched eta manifold, bored to mate to an i intake, flows almost as well as an I intake? Longer runners usually help mid range too, right? Or am I way off here?
The eta manifold bit is not an upgrade over a 2.5 setup. We did some dyno testing of various combinations. If you have an eta (pre-1988 with flat pistons) and add an 885 head, it's an upgrade. Adding a 2.7 bottom end to your 2.5 equipped car is a downgrade. The 885 top end on a 2.7 bottom makes about 140whp/145wtq. Take that same 2.5/2.7 and put the eta manifold back on it (no runner porting) and use the "i" TB, then the HP remains the same, but the TQ will increase about 25 at the wheels. Our example made 145whp/170wtq. For comparison sake, a healthy stock 2.5 with all accys and stock exhaust usually tips the dyno around 145whp/145wtq and 155/155 or so in Spec trim (used solid engine).
That's awesome info, I've been looking for dyno tests like that for a while (haven't been looking very hard though). To be clear, 2.5 head and block with eta manifold doesn't gain much, but if I did the same with the eta bottom end it gains a bunch of torque? And you didn't even touch the intake ports? That's very interesting.
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It all depends on what you are starting with. If you have a 325i, then leave it, there's no factory parts that will make it better. Never tried and eta manifold on a 2.5 as it would just choke it down.
You just said that adding an eta manifold to a 2.7block/885 head increases tq without a loss in hp. In fact, putting out the same hp a stock i puts out. Since it flows enough for 145whp, where is the choking coming in?
In fact, putting out the same hp a stock i puts out.
Not really. 145/170 was max effort using stock parts in race trim. A tired b25 does that HP easily.
Now sure, TQ increased, but if I do all the same things to a stock b25 that was done to the eta/885 combination, we are closer to 170/170 from a .5mm over stock-cam b25. So, we have to compare apples to apples. Just as much TQ as the 2.7, but 25 more hp that covers more RPM.
With a proper seta (with a b25 cam), 170whp/tq is easily made.
Be interesting to see what would happen if an eta manifold was plugged on a 2.5, but I have a feeling TQ peak would increase lower in the RPM, the HP curve would fade at or under 5500rpm (vs the 6k+ of a 2.5), and total power curve will be moved down on a graph.
The peak numbers from memory don't tell the whole story. I've tuned cars that only increased peak by 1-2hp, but when overlaying the graphs, you can clearly see 30+ hp/tq increases in some areas.
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