Mandic 0 Posted May 11, 2007 Hi, Has anyone flow tested different bore diameters on Mi16 head? 83, 85, 86, 88mm? I'm interested in how shrouding affects flow. Cheers Ziga Share this post Link to post Share on other sites
eeyore 0 Posted May 11, 2007 when going from 83 up to an 88mm bore on my mi16 i opened up the chambers to the new gasket line to hopefully de shroud the valves, i didnt flow test it but the tourque was realy good (205lb ft) the 1900 engine with the same head, cams, inlet, exhaust, etc peaked at 160lb ft and was generally not nearly as impressive. somethings obviously working! Share this post Link to post Share on other sites
Robsbc 0 1 Cars Posted May 11, 2007 when going from 83 up to an 88mm bore on my mi16 i opened up the chambers to the new gasket line to hopefully de shroud the valves, i didnt flow test it but the tourque was realy good (205lb ft) the 1900 engine with the same head, cams, inlet, exhaust, etc peaked at 160lb ft and was generally not nearly as impressive. somethings obviously working! Don't forget your 88mm bore engine has different stroke it was like 2.3L compared to 1.9L. Share this post Link to post Share on other sites
B1ack_Mi16 67 Posted May 12, 2007 Don't forget your 88mm bore engine has different stroke it was like 2.3L compared to 1.9L. It was 2238cc if I remember correctly. Still 2238/1905 * 160lbft = 188lbft so 205lbft is certainly good. Share this post Link to post Share on other sites
eeyore 0 Posted May 12, 2007 yes it was 92mm stroke and 88mm bore 2230 as you rightly said Share this post Link to post Share on other sites
petert 554 Posted May 12, 2007 The Mi16 head definitely flows better on an 86mm bore, especially with 36.5mm valves. Whilst I haven't done any true A-B testing, the results from 86mm suggest it seems "easier" to get better results on the bigger bore, particularly at higher lifts. So much so, that we even "tweak" the liners on 83+mm liner engines to match an increased unshrouding of the chamber. A special thing that can only be achieved with a copper head gasket. Share this post Link to post Share on other sites
benlilly 0 Posted May 13, 2007 The Mi16 head definitely flows better on an 86mm bore, especially with 36.5mm valves. Whilst I haven't done any true A-B testing, the results from 86mm suggest it seems "easier" to get better results on the bigger bore, particularly at higher lifts. So much so, that we even "tweak" the liners on 83+mm liner engines to match an increased unshrouding of the chamber. A special thing that can only be achieved with a copper head gasket. Hi Peter, Do you have any photos of this tweak or can you post a drawing? I have a 43mm 8v head and the shrouding on the one side is really bad. Would like to improve it. Share this post Link to post Share on other sites
Mandic 0 Posted September 6, 2007 Reopening topic... Has anyone done any flowtests with different bore dia on Mi head? Especially with 3 angle valve seats? Thanks Ziga Share this post Link to post Share on other sites
Mattsav 1 Posted September 6, 2007 Without modifying the chamber there's very little difference. Share this post Link to post Share on other sites
Mandic 0 Posted September 6, 2007 Chamber? Something slipped my mind right now, Puma once said that he was doing head work without any real benefits, then someone told him to start somewhere else, which at first sounded weird to him. Now, does this happen to be it So You're saying the key to Mi16 flow lies in chamber mods? You've once posted Your job's flow results, any progress from back then? Interested to see, as I'm looking for a person to trust my Mi16 head to for quite some time. Cheers Ziga Share this post Link to post Share on other sites
Sandy 189 Posted September 7, 2007 We had a 1.93 36.5mm valve Mi16 in for mapping the other day. The results were very good, but i'm not sure there's any significant end benefit to the bigger valves in reality. here's some results from SRD's rollers, similar conditions. Engine 1. 2 seasons old, originally made 200bhp at wheels, but breathing down a bit at the time of testing. 83.5x88mm 1930cc Standard 34.5mm valves JRE cams/solid lifters Ported head High comp forged pistons Wet sump 48mm DCOE bodies 90mm trumpets, re-angled Longman inlet manifold, twin injectors 2.5" exhaust Engine 2. Freshly built/run in, good cylinder condition. 83.5x88mm 1930cc Puma 36.5mm valves Cat cams/solid lifters Ported head High comp forged pistons Dry sump 48mm DCOE bodies 90mm trumpets, Longman inlet manifold, single injectors in bodies 2.5" exhaust RPM---Engine1---Engine2 5000---127---125 6000---166---158 7000---183---180 7500---180---192 I think the results are close enough to be tomato/tomato really, in which case the extra work of 36.5mm valves is of debatable value. Share this post Link to post Share on other sites
Mandic 0 Posted September 7, 2007 Well I'd kinda like to understand why is Gti6 head so much better than Mi's. Have seen RR reports of Kate's engine and must say I'm impressed. Where is the extra flow comming from? Surely bore dia and valve seat angles have their effect, but to such extent? As a Mi fan I'm willing to spend some money to make head better, to outflow Gti6 head. But if it can not be done, then I'm more and more thinking that Gti6 head is the way forward, regardless of what is stated on paper, and what should and what shouldn't work on paper, ie. bigger valves, better flow capabilities, high valve lift flow, ... Cheers Ziga Share this post Link to post Share on other sites
bren_1.3 1 Posted September 7, 2007 is that a typo at 7500rpm sandy? 7500---190---192 ????? Share this post Link to post Share on other sites
Sandy 189 Posted September 7, 2007 No that's right, 180---192, engine 1 definately rolled off a bit at that point. Bear in mind that engine 1 was making 200 at the wheels (at Emerald) when it was fresh and it had doen several seasons without major work, so it's probably dropped off a fair bit at this test. My point is that the claims made for big valves, don't seem to come through in reality in this case. Also consider that Engine 2 literally has as much lift on overlap as is physically possible without valves clipping, which makes cam choice very limited compared to standard valves. They're both strong engines and perform well, but the extra theoretical flow of the big valves, isn't manifesting as a tangible improvement in power or torque. Share this post Link to post Share on other sites
James_R 3 Posted September 7, 2007 I've got a bench flow test of my GTi-6 head on an 83mm bore (As I was going to use it on an Mi bottom end) and it out flows a Big valve flowed Mi head to 11lift (ish) then the Mi takes over from 11-14mm lifts. It's really impressive the difference and puts question marks over the PumaRacing valve theory. More port shape it seems. Anyways given the choice I'm using a 6 head, it's just getting hold of them easily and a spare Share this post Link to post Share on other sites
Mattsav 1 Posted September 9, 2007 If you have a choice of mi16 or GTI-6 head then the Gti-6 head is far superior. The GTI-6 head has 34.2mm inlet but fitting 35mm inlets and modding the head to suit gives BIG flow gains from off the seat to around 12.5mm of lift (the GTi-6 head seems to be made for a 35mm valve) Plus the cams are cheaper and stiffer so you can run more valve acceleration. You can see the effect of the low and mid range flow when comparing Kate graphs. The Mi16 head has one major flaw which they got right with the GTi-6 head. Share this post Link to post Share on other sites
Mandic 0 Posted September 9, 2007 I'll give a shot And what is this flaw? Do You sell/stock those 35mm valves? Thanks! Ziga Share this post Link to post Share on other sites
