ozconnection

Well, I changed over to a 190 degree F. (88 deg. celcius) thermostat today. The 160 degree F. unit was removed. I was actually going to test the block/head water pressure but did the thermostat instead! (In retrospect, I should have done this first, to get a baseline pressure reading. Still it can be done, just a bit of extra work that I could've saved myself. ) How does it run? Pretty bloody good, actually. Tip in response could be a little hesitant at times with the cooler thermostat, with the warmer one, I didn't notice any at all. (vaporising the fuel better perhaps?) I can't really test it with the G-tech because there are heaps of radar traps and patrol vehicles around ATM. Christmas time I guess. Double demerit points too. The disconcerning thing about having such a hot thermostat is the position of the needle on the guage, it's 3/4 hot!! But it's stable. The cabin heater works brilliantly. Tomorrow I'll work on testing the block pressure to see where it is. After that, I'll start with advancing the timing to see what happens. Todays setup was 15 degrees static, 35 degrees total @ wot and above 3500rpm and with the vacuum advance connected to manifold vacuum so idle becomes 31 degrees @ 850rpm. Todays efforts didn't cause any rough idling or any pinging. So far, so good!

I did....once. Don't go too tight, sure it's quieter but you can introduce other problems like poor manifold vacuum, rough idle and in a worst case scenario...burnt valves and valve seats. I had the first two symptoms and figured something wasn't quite right. Nutted it down to too tight valve clearances done by me! Once adjusted and the engine running properly, I could live with the little bit of extra valve train noise.

I was, until recently, an OH&S officer at my work. One poster I put up on the wall I remember particularly well. Oxygen + Heat + Fuel = Fire Remove any one of these and the fire cannot exist. Sure the spark plug initiates the 'fire' in our engines, but what happens to that fire following initialization? The chamber has just been blasted a relatively cold charge of air/fuel and the spark plug fires for only a fairly brief period of time. To continue the combustion process, heat is needed in the chamber. What temperature (and pressure) is best at that point? To investigate this, I'm suggesting we play with not only the ignition timing point but also the surrounding ambient temperature (and pressure of the cooling medium) around the combustion chamber to try and get to where we want to go. To quote the characteristics of other engines is taking a shortcut to potential misinformation. We need to explore the characteristics of our engines for themselves. Even if I find my ideas to be heading in the wrong direction, at least I can say I've done it the Aussie way and "Given it a shot!' Friends, what do we have to loose by trying?

I like to challenge convention and will ask the question: Does a cooler thermostat benefit the running performance of the engine? OK, the way I see it is a cooler thermostat opens at a lower temperature. At that point, water is allowed to circulate through the radiator etc. The temperature of the coolant at that point is less because it hasn't had as much time to scrub off as much heat from the engine. But probably more significant is that some of the coolant pressure needed to keep the engine from forming steam pockets is released by the thermostat opening 'early'. So, can one assume that by increasing the opening point (temperature) of the thermostat, there is more time for the coolant to absorb the heat from the engine whilst also maintaing a higher coolant pressure in the coolant passageways around the block and head? Or does it make a difference at all when the thermostats are open in both cases? I managed to also find a 190 degree thermostat. Seems I got it a bit wrong, the 160 degree unit is not listed as a stock temperature thermostat. 190 degree cold climates 180 degree normal 170 degree tropical climates. My guess is that if I were to use the 190 degree thermostat, my engine will warm up more quickly. Less wear can only be a good thing. Engine oil needs to be around 95 degrees celcius minimum from what I understand. To me it kinda makes sense to keep the coolant close to oil temperature when not at WOT for a streetcar. Then when you open the throttle up, temperature of the oil is where you want it, it hasn't cooled off from slow rpms and closed throttles/low loads. I'm willing to try this out during the week. After the change, I'll see if I can't advance the timing further. Call it an experiment if you like. The thermostat cost me AU$13.00, about US$11.70. That's not much!! Coolant and gasket I already have. Cheers!

I can feel the difference at part throttle only, but nothing much changed at WOT. (Can a G-Tech tell the difference between 125 and 130 rwhp, for example when pushing along 3200lbs of Cedric!? ) I'm curious about the thermostats because of the amount of temperature variance there is between the ones I've seen (and used) for L engines. 161, 171 and 181 degrees F are available to me here in Sydney. I'm currently using a 161 degree unit. My factory temp. guage stays just on the cool side of halfway. The others move the dial to midway with the 171 thermostat and to the hot side of halfway with the 181 degree thermostat. My point? Can you put in a different temperature thermostat and notice a performance difference to the engine? Should the high compression guys who are having knock issues play around with different temperature thermostats in an attempt to be able to run with more total ignition timing? Hmmmm, I seem to recall from my own experiences on the dyno that I had a hot (181 degree) thermostat in the car when I put out my highest power figure a few years ago. I changed it some time later and didn't really give it too much thought....until now!! Hmmm, its not too late for me to find some this afternoon........ What do you guys think?

Great summary! I tried your suggestion of advancing the timing and it seems that I was already 'at my best' with a static of 15 degrees, 35 total. Any more and the engine would rattle when I was deep into the throttle. Did I notice any power gains? Well I did a G-Tech test and there were no changes detected by the instrument. Personally, I felt that the engine had a little more torque at part throttle but that didn't translate into quicker or faster times over the 0-100km/h sprint or 0-400 metre run. To be totally honest, the advance that you were suggesting seemed somewhat ambitious but I'm always open to reasonable suggestions and this one was quick and easy to try out. Oh well, didn't work. Just curious though, what temperature thermostats do you run with the amount of advance you suggest? You also linked this idea to a thread that talked about cylinder head/engine block coolant flow. I just couldn't find much reference to coolant pressure inside the block and head. I mean, the radiator cap will release at about 14 psi but the pressure in the block and head channels should be optimally higher at arounda 30 psi. The combined use of 'restrictors' and varying the water pump speed (great if you can use of one of those electric L series water pumps) could potentially be the key in reducing the speed at which the coolant travels around inside the engine and the restrictors helping to adjust for block and head coolant pressure. The correct coolant pressure AND flow will drastically help to stove off the formation of steam pockets, the cause of local hot spots and detonation. If that still doesn't quite keep the engine temp. stable, time to add a larger radiator. The cooling system will then operate close to or at maximum efficiency, regardless of the engine speed (with the electric pump). How many people have attached a pressure guage to the coolant passages inside the head or block to see what they are and adjusted them to get 30 psi or so?? How many people have played around with water pump pulley sizes to get the water pump to spin at its 'best' non cavitational speed? Has there been a change to a different harmonic balancer with a differently sized pulley, changing the 'ratio', either slowing or speeding up the water pump speed? I have a few things on my 'to do' list for next weekend it seems. Can't wait to discover if work needs to be done to something that I assumed to be right in the first place!! Maybe then I'll be able to run 42 degrees total advance (or 10.5 or more compression with a different cylinder head).....who knows?? Top thread, this is really thought provoking!

It seems you guys have a bit of a QC problem unfortunately.... Interesting read and perspective though. Cheers

Check this out

I've attended and participated in many Z car club dyno nights here in Sydney. I too cannot recall any L2X's make over 140 rwhp. The most I think I ever saw was one guy with a 280zx and an aftermarket management make 95 rwkw's which is about 127 rwhp. Even my own efforts with a stock cam/head and CR grossed out to 90 to 92 rwkw's (through a L4N71B auto) which I thought was pretty bloody good, since I started with a bone stock N42/N42 combo with a 2 barrel downdraught Hitatchi which dyno'ed at 60 rwkw's Can anyone prove us wrong?

I can't get the idea out of my head about running up to 42 degrees advance. Thats heaps!!!!....too much if you're going by the established 'rules of thumb' suggesting 38 degrees total advance (dta) is enough. I'm going to give it a try though, bumping up from my current 35 dta. I'm going to disconnect my vacuum advance mechanism during these tests, just to be safe. Should be very interesting! Pete, your dyno graphs are what we're after, but that pig rich mixture on the second graph/engine isn't really close enough to the other AFR's to say that there's that much of a difference in engine output, based solely on quench setups. Sure, the AFR's from both engines will never be 'exactly' the same, but I feel they're too different to sell the whole story in this case. Don't get me wrong, I'm a subscriber to this arguement though and interested in hearing from more people on the topic.

Yes, auto's do suck up quite a bit of power, about 10% from what I've read and seen. My engines were never built for outright power, more of a bias towards torque for my heavy car and auto trans as it turns out. For what it is, still goes alright....

At some point in this process, you have to turn the crank to drop the 'other' pistons down their bores for grinding........good luck with the timing chain!

Excellent summary! You said you're going to change heads. Which head are you going to use and what will be your resultant compression ratio? To get your engine to rev harder at the top end, a bigger cam would theoretically work (and to rid your engine of that pesky ping). Knowing how much bigger is the trick here. We can all work out what will/won't happen if the wrong cam or a too small one is selected. The other issue of low rpm response raises a concern if there is to be any of it left after the bigger cam is put in. Some people don't mind this trade off though. I'd just like to add something here that may be of interest. I recently was experimenting with my induction system. Changing manifold/carbs brought about pinging on my engine that I didn't have before the experimenting began. No other changes were made to my engine other than to change some of the bolt on hardware. Once the engine started to ping, I tried lots of things to try and eliminate it, without success. As soon as I installed my original hardware, the pinging ceased immediately! In retrospect, the only reasonable explanation was that maybe the engine didn't need more than 28 degrees total advance...that was my total advance on a 8.3:1 comp motor, the experimental induction system so efficient, craming in the air/fuel, it was the ignition curve for that combination that was all wrong. I guess you've seen diagrams of the ignition curves of EFI engines...they look like the mountain peaks of the Andes rather than the slopes and plataeu's of the Sahara. Maybe more work should be given to the ignition setup before abandoning the idea of higher compression and installing a head or bigger camshaft that will give less static and dynamic compression. What are high performance street guys running 10.5 or more compression doing about this problem?

Wow, that's impressive! Stock cam? Stock head? Stock exhaust? Stock ignition? Manual trans I guess? To quote a rear wheel power figure and help this guy out ya gotta be more thorough in your description. What you've supplied if so thin, its worth basically F.A.!! Hell, I wanna know too how you got your power, so do tell.....all. I worked hard to get over 135 rwhp on my auto trans L28. Head, cam, exhaust, ignition, induction...all systems were modified, so you can see how surprised I was to read your figures without qualification.

Good question. Out of the three L28 engines I have, they're all N42. So I can't chime in. All that I can say is that even the N42's are cast differently on the spark plug side, depending on production runs/age I guess. My 'early' N42 has no square boss at all where the oil filter goes, the other two do. And the ones that have the square boss are all drilled and tapped and have four holes.

Oh dear, the other day it was inflatables, today its VD's and crank stroking......Tony, you need to get home ASAP and 'tend your flock' me thinks....badly Cheers mate.

You're actually right. The Tem-coupled fan that Nissan uses for the L series is quite efficient, and doesn't always draw a huge amount of power from the engine. During cooler weather, the fan will not operate too much at all, but as the seasons get hotter, the fan has to work harder and thus more engine power is consumed. Sure, there will be a greater current draw from a thermo or electric fan, but if your electrical system is in good order, ie battery and alternator, then all should be well with little noticable difference, if at all. What do I have on my car? A Tem-coupled fan, as original. I like the stock arrangement and has never given me any reason to change it over. If I had a machine where every last drop of power was to be extracted, then sure I would replace the fan with an electric one. Just not for this vehicle, in this case. The advantage of an electric fan is that it can be manually or thermostatically triggered. Or can be left on after a hard run to cool things down after the engine is switched off. Two things, don't forget to turn it on when in traffic and to turn it off when leaving the car for any time or the battery can go flat. A timer can be installed if necessary. It's all getting a little overcomplicated, unless that kind of thing is your thing. Your call. Cheers.

I would agree that the removal of the fan will add power. The coil 'upgrade', hardly any power added other than perhaps a 'smoother' running engine. For me and my L28, my biggest power adder was the exhaust system upgrade. (headers and a 2.5 inch exhaust with 2 mufflers) I did before and after dyno tests to prove it! The throttle body you upgraded to would be adding some power. I spent a bucket load on MSD coils and amp boxes (6BTM) with a 280zx dizzy. (No points!) Smoother, yes, more powerful?....hmmmmm not that I could tell! Cheers.

I'll second that! Absolutely! My guess is you've pulled apart the engine for nothing other than to replace parts that probably didn't need it. Sorry, but the truth man Still, it'll be fresh after you're done, like you said.

Read this and memorise Megasquirt it man! You said you already have it, didn't you? At least that's what I thought you said?

And we play around with these L Series dinosaur donks because.......? Hell, can someone please remind me!!!!!!!!! Tony D....I hate you!

Almost 100kw's at the rear wheels is a great figure. I had to work my L28 quite a bit to get there. Well done. Cheers mate.

No, are you serious?

Here in Australia, we never got round port heads until late......on some of our EFI R30 Skylines we got the N47 round port head. But as a consequence of their late arrival and very limited demand, round port headers were never offered here. When I bought one of those heads and used it on an L28 I had, I had no option but to use the square port gasket. Round port gaskets didn't exist then either down here. (What Nissan would sell you would be a gasket with the exhaust ports cut out and the sides angled, a bit like a diamond shape.) The square port gasket worked well and didn't leak at all. There is talk about a phenomenon called 'anti-reversion' and some guys actually build headers to take advantage of this. I think that by using a square header on a round port head can mimic this. I have no hard evidence for you but the theory seems to hold up when you look at the parts. It certainly didn't drop any power when I used this setup. Cheers.