Lazeum

Low fuel pressure is most likely not what's causing your problem... That's my point of view. It would be helpful to start by knowing the jets sizes (idle jet, main jet, air jet, emulsion tube & choke size) you have in your carbs, check as well the float level - make sure it is the same for all of the carbs. Backfire could also be due to bad timing. I would check timing & distributor with a timing light as well.

You should go and search on the forum for people with Webers & other triples to compare your setup with the ones' from others. You'll find the answer to your question. You'll see that we do not always agree about what would be required. As far as I'm concerned, with stock engine and supportive mods, you'll be fine with DCOE40. The risk of having too big carbs is low torque at low & mid range => not fun Too small carb and you won't get HP at high load but engine would be fun at low & mid RPM => still fun Afterwards, you can run big carbs with small venturi/chokes, so it trully depends on your hp goals on the long range and how you expect to run your car (street / Track....?)

After some discussions with some skilled tuners, it appears an independant knock sensor is a "must have". On Silvias with SR20det (my DD), knock sensor is very inefficient so relying on stock system is a mistake. Thus, I have made my own based on tuners input. I did not have the opportunity to try it yet but this solution seems to be one of the most reliable. Electronic versions have to filter signals to extract knock from white noise. Being an NVH engineer, I know it is not an easy task. It is perfectly doable but it requires some time and skills (=$$$ for final customer) from manufacturers. The filtering can be done naturally with your ears on mechanical versions (I once found on youtube some clip of knock to ear it)

Even it is "possible" to do it on the road, I agree with Tony, best solution is a dyno Â

Regarding turbos & boost, I would try to find the compressor map of your turbo and get the boost were it should be to get the most of your turbo (injectors, IC & fuel system should follow as well obviously) Then, I'll get the ignition tuned up properly with a close eye (or ear!!) on detonation, ignition is where you'll find the most of the power. For this matter, I've made a DIY detcan for less than $15. A dyno session or some pulls on highway ramps & some steady states log sessions with a friend to help would do the trick.

...or you can get the megajolt jr. kit for half the price + EDIS (80$) Â This is one of my project in the future.

 If you can feel better I was visiting the US for 2 weeks in August (I now live in Europe) and I was looking for a GM 3 Bar MAP sensor. I ordered it at Advance Autoparts, they were supposed to call me when they would receive it Thursday of my first week. I had to pay to order it. I went to see them to grab the part the next Friday with the receipt; they never called me. The lady in the store told me the part has never been order because my receipt was a regular receipt, not one for part ordered so I had to order it again, lead time was 8 days. The guy who made the order for me screwed up. Bottom line is I left the country even before the part arrived so a friend of mine is taking care of it now and I still don't have my sensor to map the car... sh*t happens but I don't think we can blame the whole organization for the mistake on one individual.

When you said it has been done, did people use the braces the same way as the one on the picture? Does this kind of products exists for s30? I also understand the OEM specs about this particular area but I'll be questionning anyhow the crush mode of the s30, not sure it will prevent anything from saving my life if crash is bad enough to bend this area (the engine would have a lot of opportunity to come into the cabin anyhow) I guess I will add it to my to-do list when time will come to refresh the body ("no rust" - I can see - but never has been restored)

I had a discussion with some friends about fender braces on Mitsu Evos forum. I've never heard of such parts before and I'm very suspicious about the benefits of those parts. By searching online, I found some great comments about them. So I'm wondering why aren't they popular then on regular suspension mods? As long as you can weld, those parts look quite easy to do and I've never seen them on s30. To get the same stiffening effect, I've seen many members having a tube going from the strut tower to the top of the firewall (either to the center of the firewall or to each side of it). Comments from Turbo Magazine A picture from the thread below to show the product... (the product looks kind of "weak" versus the rest of the car) Basic changes are better steering feedback as well as better stability when braking/cornering. I guess it could be worth a check... The links I've read.... on Evos, Silvias, RX7. http://www.turbomaga...tem/nagisa.html http://forums.nicocl...ll-t255621.html http://www.rx7club.c...ad.php?t=642616 And the part source... http://www.more-japa...-p-2-c-281.html

I haven't been playing with distributors with advance before but Vaccum advance is effective when you get some vaccum in your intake (obviously). At WOT at the dyno, there isn't any vaccum since everything is wide open between your intake and the atmosphere. It should make no or very small difference to have your vaccum port plugged or not at WOT. Vaccum helps pulling timing when you're cruising to help MPG. That's my understanding of Vaccum advance systems, we don't use it with Triple Carbs but it could probably help smoothen up the engine at low load. Afterwards, you've experienced some weird results, it might be because you've passed MBT (Minimum Best Timing), all fuel might not have time to get fully burnt resulting in rich exhaust gases. Have you got some data to confirm or discard this hypotesis? Several Torque Curve vs. Timing @WOT for instance?

Have you played with the timing? you most likely have changed your CR & engine efficiency, timing would need some adjustment if it was not done, you might have some power to recover. Regarding head design I've been from a stock N42 head with Schneider cam to a P79 made by Braap with Rebello cam, difference was small until I bumped the timing to where it was supposed to be, difference became huge..

The point regarding the "idle speed screw" from Bjhines is because people tend to use this screw to setup the idle speed whereas it is used for sync between carbs. You will see people having their throttle plate opened way too much to get right idle speed because of misunderstanding of the physics of the carsb. Regarding the sync between the carb, I also have a synchrometer but I end up using a fuel or heater hose to listen to the suction of air. All carbs should be even. Some poeple don't like this method, personnaly I had great results! Go slow and since it is difficult to damage anything at idle, just try stuff and see what happens.

Ok, it's clear now (I was double guessing my English vocabulary)

A dumb question: What do you call the trans mount? Is it the bushings/mount that hold the transmission (=gearbox) to the body or the front bushing at the differential with the cross member being the piece that hold the front bushings of the rear control arms? Like everybody else (almost!) I do also have a clunk. That could be something nice to check... My whole rear end however is new (front diff bushing, mustache bar bushings, etc...)

I actually love decel lean pop too! Sounds like the race cars I have seen recently at Le Mans Classic (GT40's, Porsche 904 gts, etc...) I've been also wondering if it could hurt the exhaust valve with resonance and back pressure in the exhaust system...

 I'm quite curious to follow this thread and see how it would be resolved If your narrow band is reading lean, it would mean you're above 14,7 AFR???? that would be super lean! Since narrow band are either rich or lean, there isn't much in between! How does the spark plugs look like? are they all white? That would confirm or not what you're seeing with the narrow band. Personally I don't believe you can run at WOT with boost and lean AFR above 14.7. I would start looking at ignition & timing for sure. having some missing might make your AFR looks lean. If you have an air leak, could the ecu be able to retard the timing to avoid knock? You should run a boost leak to check that. It has to be big because a small air leak will make your engine to run too rich; the MAF will see more air coming into the intake than what is really going into the engine, so fuel will be in excess. Good luck!

This is true only for US Here in Europe, 240z has got rear sway bar since the begininig but the fixtures were different, there were 2 brackets that hold the stab bar in front of the rear suspension on the 2 lateral frame rails.

Vid looks good with quite responsive engine I'll think about what I want over the weekend but I want to keep a car with high torque at low rpm instead of max HP, of course if I can get both, I'll take it! I could consider also 45DCOE. I'm located in europe so I guess it is a little easier. There're 2 new 45DCOE for 500€ for sale for instance now. However my intake manifold, a Cannon unit, has some runner that are smaller than 45 sio I'm wondering if it would make sense to go with them as straight remplacement from 40DCOE. So porting might help solving this issue though.

    I'm glad to be part of that club. I knew choke would be too small but I did not think it would lead to such a rich mixture. I run out of jets, 130 are the smallest I've got so next step would be shopping (or money to spend from another point of view) I might try smaller idle jet, I'll have to look for what I've got, I'm not so sure about my jet library. The goal is to get a street car with a lot of torque, so 34mm choke would be my next step. If I have to go to 36mm, I'd rather go with 45DCOE, I beleive the ratio choke vs. carb diameter is important. As far as bottom end, I've got a rebuild stock L28 overbored to 0.5mm.

I've read if chokes (venturi) are too small, it could make the engine too rich no matter what   What do you think about such remark? The source; the text is on the lower section of the page above the choke size table.

Thanks Tony for the comments It feels good to have this issue sorted. I've learned in the process how to root cause an issue such as this one. It would be good for others to know the tricks instead of shot gunning the problem. I've been running the Z this weekend, I'm still anxious to turn on the lights but it has worked like a charm. It better does since I'll be driving the Z at night next weekend.

since my last technical post, I've changed my head with Braap's custom P79 head & Rebello Street assymetrical cam grind. CR went from 10.3/10.5 to 9.3/9.5. Flow/efficiency of the head is now much better than my previous stock N42 head. So it is now time to tune again the engine So far, I've just spent time making the engine run, idle has been setup correctly. I had to get smaller idle jet than before. My setup as of today: 40DCOE 32mm choke 45f9 idle jet 45 accel pump 135 main 180 air F11 emulsion tube Float height has been properly done and adjusted when carbs were out of car during head swap. I wanted to try to setup the engine by using the original mech pump. this weekend I found out engine was running out of gas on high gears. So I've plugged my Electrical pump (Carter unit SUPER loud) Before any comments on AFR, I can say engine is quite responsive, no stumbling, chasing or whatsoever. I can hit the throttle at low rpm, car goes quite nicely. Power is good but I'm sure it could be better. The Z is faster than my Dad's BMW Z3 with 3.0L L6 (231hp) to give you a comparison point. However, Engine is smooth except when cold, choke is required to avoid the engine to stall. When hot, engine idle is set at 800rpm. I've done some AFR log in 2nd gear, fuel pump should be out of the picture since there's not enough time to get fuel starvation with empty bowl. However, low fuel level in bowl could have an impact on AFR. Fuel supply setup used is electrical pump next to the tank with still mech pump attached to the system followed by a fuel pressure regulator setup at 3psi. I'm currently wondering if it could be a restriction in the system, it will be removed anyway very shorly so I will find out. AFR were super rich in low/mid range & very lean in high rpm. So I've switched my main jet with smaller ones: 130. Here's the log. I'm quite consufed with the results. It means better head with high flow & better efficiency requires much less fuel than stock head???!! I would have expected the opposite quite frankly. Could it be the back pressure being so much greater that it makes the engine sucking much more fuel thru the same jets size? I've been questionning the results from the wideband but the exhaust tip is really black. Spark plugs however are brown. Based on the results, Main jet required would be in the ball park of 110/120. I've never seen an engine running such small main jets (I don't have a lot experience yet though). If my engine needs those to be happy I'll go with it but I need to source some parts then.Main jets would need to be smaller too to richen the AFR at high rpm, I've got 165 air jet to try. I'll see how it goes. Regarding idle, it is also very rich at cruising speed, I run around 10.5/11.0 AFR whereas idle screws are 1.5 turns from being close. since idle screws are fine and cruising AFR is super rich I'm wondering if I should not deviate from xxf9 idle jets and try something else with bigger air bypass hole (f6, f8 ?????) I need to investigate on this one. It is also difficult to predict yet since AFR is not steady at all but it seems I've lost the rich spot at 4500rpm. Leadings me to think it is intake geometry related since carbs & manifold remain the same. (see page 13, post 312)

I had a similar issue no later than last week: no power in 3rd gear and higher gear, tach bumping with low rev. Engine setup is L28 with custom head, 3x40DCOE, NGK BP7ES all gapped at 0.035", Mallory Unilite ignition with Mallory HyFire 6AL (MSD 6AL equivalent), 5sp + R200 3..9 I found out the connection to the resistor was almost cut, one or two wires out of 10/15 holding the connector remained ok. I fixed it, rev is now steady. Regarding the loss of power, I found out I was running out of gas. It does not happen in lower gear since there's enough gas in the bowl for the quick accelerations that does not last long. I then connected an electrical pump to support the mech one, problem is now solved as far as I'm concerned (I will removed the mech one since it could be a restriction now in my case) So I believe in your case, it could be the pump (elec or mech) that starts to go bad or which is not sufficient. To try that I would suggest releasing the gas pedal for some seconds when you got the issue you've described and try to accelerate again afterwards since bowls should now be full again.

I just wanted to let you know, everything is now working very well I've put 15A fuses instaead of 20A since I couldn't find any. I don't think I've been dealing the right way with electronically issue. I should have removed all the bulbs from my car, check if fuse was still blowing with no bulb, that would have meant problem was with wires. I should have afterwards put bulbs one by one until I'd have blew a fuse. It would have been much quicker than guessing and trying to solve unproven issue. Anyway issue sorted, it was ignition switch corroded, NOK side marker bulb & wrong installation (wires mixed up) during the check up. thanks for your help!

I'm by no mean what we can call an expert but I deal every day with underhood applications and rust protection (ME in Steering systems). So here's my little experience. There're many kind of rust protections: one is to seal the metal to oxygen to avoid oxydation (powder coating, paint, etc.), the other one is to get the protection to "rust" prior to the metal (this is what galvanization is all about) The big difference is if you scratch or chip an area of your powder coated part, it will rust again. Since powder coating is quite hard, most of the time it will be very fine but if you got a rock hitting your part with high energy (speed) it would happen. A control arm is most likely the kind of part that might get this kind of condition. On the other hand, galvanized part are having a sacrificial protection, meaning the Zinc & Alu contained in the coating would rust prior to steel. this will create some white rust that will show up before the red one. The white one will also seal the area. This protection (cathodic protection) will insure that even if you scratch the part and expose steel, it will not rust. Based on what I've told you, you know how I'm going to work on my suspension parts You also have hot and cold galvanization. the hot one you can dip the part in hot "bath" of Zn, spray it or use electrolysis then you'll have to cure it in an oven (to get molecules organized), the other one is a cold one, not as good as the ot one but more practical which is nothing more than Zn mixed in resin. I found some in hardware store. Nothing avoids you to paint the part on top of it (make sure to pick an appropriate paint) that would make the part even more resistant to rust. Another drawback from galva is the process might fill out hole and small details. In some cases, drilling is required to bring original part back to spec. For your understanding, here's a link to one of my supplier explaining their process (I'm such a nice customer )