Long rod 4A or how to destroke a 7A

[trdee]

If you want to make ignorant comments you are going to get shot down buddy. This is the tech section, not the "OMG THIS IS SO COOL IM GOING TO VOMIT A RAINBOW OUT OF MY MOUTH" section

edit; and before you start with the "you dont know ae86s" rant, i have driven 86s quite a few times, and my friend's sprinter has a smallport 4A which makes 118rwkw at 9000rpm and revs to 9500rpm, with stock crank and rods, and has been doing so for quite a long time too I've driven it plenty of times, both on the street and on the track, and it is very much on the upper limit of what I would consider a streetable engine. I have owned and modified A-engined vehicles for almost 7 years now too, and have either owned or driven every variant of 4AG, from the bigport through to the BT20V, every variant of 4AGZE and various different turbo setups as well, both standard and highly modified motors of every kind. So I have a fair knowledge of how these engines behave under various states of tune in FF, FR and MR vehicles...

Your comment mentioned building an engine as far as it would go, and referenced 10krpm and above. At these revs, as mentioned earlier, and as has been documented significantly elsewhere, you need to do serious mods to the oiling system for it to not shit itself immediately (dry sump systems arent known for their long term reliability either BTW). You also need to use very high compression ratios and large cams for it to make power at or above these kinds of revs, which make the car a piece of shit to drive in traffic as well as considerably decreasing its fuel economy. These kinds of revs will put shit tonnes more strain on bearings and rings as well, regardless of how nice your r/s ratio is, and will decrease engine life accordingly.

Your "if you dont like this, you dont understand 86s" comment was just the icing on the cake

[Sam_Q]

bermy and Trdee: what's wrong with the stock 20v oil pump and TODA gears? from what I understand it's happy sitting at 10,000rpm without oil pressure loss.

[trdee]

It's not so much about the oil pressure loss as it is about the gears shattering. My mate's 4A seems to be doing ok revving to 9500 on a stock oil pump but there are a fair few other people out there which have had gears shatter at sustained +9000rpm running.

I don't have evidence but, I would suspect that engine harmonics probably start playing a significant role at these RPMS and are the likely culprit for said oil pump kablammo shenanigans. I'm sure I've read about it somewhere before in the past, but yeah, dont have anything in my tech archive...

[bermy]

^^^What he said... first the 20v oil pump is just the same 19036 pump found in the redtop engine. The blacktop has that stupid hydraulic bender to keep the timing belt under tension but it's not any different from all the pump fitted on 4A since 1990. The toda might be a little stronger since it's supposably made from better material, but the trouble with all crank mounted oil pump is that they all get the harmonics of the crank, all 100% of them without attenuation, which get pretty devastating at higher RPM. I know for sure that using those shinny T3 aluminum pulleys is probably the worst thing you can do on such an engine...

Just for reference this is what happened 2 weeks ago to my friend's SR20VET oil pump after revving it under 8000 rpm with a solid alloy pulley



...and I've seen that in 4As too many times. The stock crank pulley does it's job but when you get outside the engine normal range of operation, it's like playing russian roulette. Like said above, it will sustain a little 9000rpm rev (more so if free reving) but get the engine under load for some time as such RPM and you're just asking for trouble. An aftermarket ATI damper might be able to help a little in that department but once again it doesn't change the fact that the oil pump is directly driven by the crank... ask RB guys what they think of their crank mounted oil pumps

This is why even if I don't plan to push that thing above 9000ish RPM my oil pump now has this in the outlet...



...that my lower oil pan looks like this...



...my windage tray like that...



...and my crank pulley like that



It is still a standard wet-sump system but it uses an externally mounted pump underdriven at 50% engine speed with a higher capacity pump, it will not just be spun to half the crank speed (well under 5000 rpm) but it is also isolated from the crank by a long toothed rubber belt. Other nice feature is that after long period without turning hte engine, you can just pop the belt and spin the pump with a drill to prime the system without having to spin the crank dry. It'll have one hose from the lowerpan mounted oil pickup to the pump inlet and one other hose from the pump outlet to the standard oil pump housing through the machining plug. It's so simple, it uses the stock pressure release valve and stock oil routing, I didn't want to mess with a true drysump setup since they require a lot of hose, fitting and an aerator tank which all create more places for things to go wrong and oil problems are never small problems when they occur, so keeping it as simple as possible while removing the darn crank mounted pump is my way of going around that problem.

Here you can see the fitting in the lowerpan and the one on the stock oil pump housing which now only serves as a crank seal mount and an oil pressure release valve. I'll probably use 1/2" aluminum flared tubes to connect the pump that'll be installed on the A/C mount because solid lines are that much better than any hose, even baller SS braided ones.



Oh and just to get the record straight, what ever you do to the r/s ratio, an engine revving to 10 or 11k rpm will have it's piston fully stop 2 times every rotation so if you take any 77mm stroke and try to smooth the acceleration as much as possible you'll still have HUGE forces that will still be very hard on the rings/cylinder/pistons. Sure it'll fare a little better than a standard 4A with it's crappy r/s ratio, but like said above, r/s ratio will not magically change those fact. To see what I'm talking about refer to the 10m long rod curve. This is a near perfect sine wave which get the acceleration as low as possible and they are still around 3400G at 9000rpm... and I can calculate what they'd be at 10 or 11k rpm but it won't be any lower than what a standard 4A sees at 8000 rpm... and that's with a 10m long rod which will probably not fit under anyone's hood

[bermy]

I (read my brother and I) are using a 3 inch stroke crank in a large bore Chev smallblock V8 with 6.4 inch rods for our compound turbo engine in the Camaro.
The rod to stroke ratio should be favourable no?

Cheers,
Jason

Hahaha, should be around that of a CBR600RR... I think you're good

[Sam_Q]

trdee: 9000RPM is about the point where they are meant to be break. The OEM gears are sintered metal and the TODA upgrade are 4130, I have never heard of anyone breaking a TODA gear set yet. I also have had some reliable information that they hold the pressure better at higher revs, they are reportedly made to a higher tolerance. That buddy of yours is playing with fire and I strongly suggest he upgrade or else he is going to have to buy a new engine when it goes.

Bermy: Apart from the welds it's a decent set up to have. I agree solid crank pulleys are a bad idea. I can buy 7m oil pumps cheap enough and I have been tempted to use one of them off the side. Where did you source the pulley and belt from? Also what holds the toothed pulley to the crank pulley?

[trdee]

trdee: 9000RPM is about the point where they are meant to be break. The OEM gears are sintered metal and the TODA upgrade are 4130, I have never heard of anyone breaking a TODA gear set yet. I also have had some reliable information that they hold the pressure better at higher revs, they are reportedly made to a higher tolerance. That buddy of yours is playing with fire and I strongly suggest he upgrade or else he is going to have to buy a new engine when it goes.

I have no direct experience with the TODA gears so I have chosen not to comment on them (all though I have heard some people say that they are not all they are cracked up to be..). I am talking about stock pumps only. Bermy made the comment on the TODA gears, I assume he has more info on the matter. Personally I would want to run a dry sump setup on anything revving around or above the 10k mark anyway, and not just to get rid of the crank mounted oil pump, but for the other issues that also become apparent at high RPMS (windage/frothing/etc).

And yes I have told my mate to get a dry sump setup a couple of times already now it seems to be doing ok for the moment, but sooner or later it will probably go kablammo yes...

[Sam_Q]

I agree, if someone has the money to build a 4agte engine that reaches or can go past 10,000 then they can and and should run a dry sump system.

As for you buddy those upgrade gears should be ideal for him.

[bermy]

Well I must apologize, I have not seen a TODA pump break... neither have a seen a TODA pump anyway. The thing is that the whole setup I'm building is worth less than a TODA rotor and it's better anytime of the day so even if they hold to higher RPM, I can't really see why I, or anyone else, would choose that as an upgrade over the stock one. It has the same volume as the standard pump, it still sits on the crank so it's subjected to harmonics, even if it holds fine over 9000rpm, give it a good ping event and it could be fubar like anything else, destroying what's left of the engine... for me taking a flawed design and upgrading the material quality to "make it hold" is not a good way to go... might as well change the design altogheter to a better one.

For the welds I really agree with you, but those pickup tube are really thin and they have been bathing in oil for the last decade and a half... isn't the best material to work with... I actually cleaned it up a little and pressure tested it to reveal any pin holes. It's leak free and working perfect... just not the nicest piece I've ever built... but it'll be covered in oil for, I hope, quite some time

Oh and the crank pulley is 100% home made with the 7A timing gear...

I used my trusty press-drill as a mill (yeah, I do all sort of crap with that thing) to machine a spacer out of the old 8" solid brake disk



That I welded it on the stock cut pulley



I then did the same with a 1/8" steel plate to get a washer to sit on top (you can see all the parts in the picture)



I then welded the washer on top of the spacer and weld it to the spacer

I then drilled the washer in 4 places with a 1/4" bit and sat the 7A crank sprocket on top... laid that on the old 7A crank to have everything centered and welded the sprocket to the washer by filling all four 1/4" holes at the back.

Result is a fully centered pulley with a 20 tooth 8mm pitch radius tooth sproket with a clean center that looks like stock.



I'll bolt everything with an M12 bellhousing to engine bolt with a custom washer which will sandwich everything on the crank snout. I'll just have to order any aftermarket 8mm pitch radius belt of the right length to fit once the pump is in place.

[racermr2]

Guys, Let me clarify my position:

The reason I am using stock size valves-THE RULES OF THE CLASS DON'T ALLOW LARGER VALVES.
The reason I stated no expense spared- Based on THE RULES OF THE CLASS NO EXPENSE WILL BE SPARED
The reason I won't use a billet crank or a MRP kit-THE RULES OF THE CLASS DON'T ALLOW A BILLET CRANK(must be a stock piece)
Lastly, I refer everyone to the last two sentences of my post. If you have info please provide same. If all you have is criticism or a lot of WHYS, please remain quiet and let those who have credible information provide their knowledge. This is not to flame any comments or castigate anyone.
BERMY: I thank you for your knowledge and your rationale. It is greatly appreciated.

[trdee]

If you dont give everyone the facts in the first place then you cant expect to get a good response... anyways this is now getting VERY off topic. Let's try to get back to the point of this thread now, there is plenty of literature on 4As out there for anyone that wants to find it

[Adsport]

racermr2: thanks for the clarification. As is the nature of the internet none of us had any idea of your premis or intention, nor that you even compete or plan to compete in any sanctioned motorsport.

Cheers for clearing those points up, if we understood the ideals behind your queries in the first instance then I myself would not have jumped to the conclusions of how these discussions usually pan out.


I am using a stock early bigport GZE oil pump on my setup. From everything that I have read on the internet- as shallow of a resource as it can be at times, it is the same as the TRD pump. My motor is making 260kw at 22psi boost, active revlimit of 9500 on demand but I honestly don't take it to that all the time because peak power is dying off. I do frequently spin it to 9000 or 9100 but that is usually to get more out of a gear ratio, mostly 2nd and third. This motor has been running for 2.5 years now with no mechanical issues other than this month the wastegate becoming over used and worn out. This is a street car, NOT a race car so it doesn't spend as much time at its upper limit as a motor in a race car would.

I don't and haven't ever experienced any fluctuation, drop or erratic behaviour in regards to oil pressure the entire time that the motor has been running. The oil pump I am using had done 101,000km when I took it out of my AW11 motor to inspect before deciding to use it in the current combination. I use Penrite 15W40 oil and an Earl's 12 row oil cooler mounted in plain front on exposure to air. I do not run a thermostat on this system either although some people argue that I should but my oil temps are very consistent and would never be considered "over cooling".

[bermy]

I don't know what pump you are talking about, but if it's one that has the square tooth design like the one on the left



Then consider yourself blessed, because those are the least desirable to have. The TRD pump was just a version of that pump with a rotor made of stronger material just like the TODA pump is a stronger version of the late model wave design.

Anyway, like said above, it may be safe or may not be but I've seen some blow so I won't trust anyone of them... the squared tooth design even less. Even toyota stopped making it in favor of a narrower wave design to replace the original pumps.

Oh and what I have against those oil pump is not fluctuating or erratic behavior, it's there tendency to explode and cause rapid and total loss of oil pressure, grenading the engine in a couple rev along the way.

[Sam_Q]

Bermy is right, you would a failure prone square tooth pump, TRD released an upgrade in 4130 but they where such a flawed design that they still broke. I can offer an upgrade pump if you want one.

Now Bermy thanks for posting the pics, very interesting and I agree with you in that what you have done is completely superior. It's also good to know those pulleys are readily weldable, although it does make me nervous doing so. I had the entertaining idea the other day of using a 7m sump mounted pump in the original distributor hole of a 16V, but Trdee is right we are getting off topic.

[bermy]

I had the entertaining idea the other day of using a 7m sump mounted pump in the original distributor hole of a 16V, but Trdee is right we are getting off topic.

Off topic or not, that's a very clever idea

BTW I have a bunch of picture comparing the early (bluetop) square tooth design with the late (redtop/20v) wave design and the 7A-FE which is also I believe the same pump as the 19025 that replaces the square tooth which is exactly the same dimension but the rotor is thinner, making the late design (redtop/20v) also known as the 19036, higher volume (probably to feed those piston oil squirter)...

...but we've sidestepped into off topicness quite too far now so I'll leave it there