Bigger cam, ignition timing question

[JMortensen]

I won't disagree, the Stock Box is unsuited to the application with the modifications as described but it most definately is not 'junk'--a stock vehicle is very well served by a Stock Box. Let's see how many MS units are around running these vehicles 30 years down the road. Durability and Longevity go a long way towards debunking the "junk" misnomer, IMO.

Let's see how many Z's there are running 30 years down the road. I'm not espousing MS as THE answer, I'm saying that stock FI and aftermarket cams don't mix. And as to the stock FI's durability, I wonder how many Z's were junked after trying to fix driveability problems that occurred due to broken connectors or bad AFMs. I'm guessing quite a few, there are enough threads about FI driveability issues on the various internet boards...

 

I stand by my previous statement:

If you want to keep your car bone stock like you said, then we could talk about the disintegrating connectors and all that, the restrictive AFM and manifold, etc. If a person doesn't mind dealing with all those issues, then OK, stock can be made to function correctly. That's about the best I can say for stock FI, that it can be made to function correctly but probably isn't now, because of the crappy connectors they came with. If you want to modify the car we can talk about how a cam install will render it basically retarded. To me, that's crappy, since I don't tend to leave things in stock form.

 

Then there is this comment:

The Megasquirt is really nothing more than the stock box set up so you can EASILY adjust what happens in reagards to inputs and outputs.

I may be wrong, and I'm way out of my comfort zone talking specifics on FI systems, but isn't the stock FI limited by the restrictive AFM and manifold, batch fire, limited ability to adjust to different engine parameters (different cams, intake systems, etc) and no spark timing capability. Doesn't MS potentially get rid of all of these issues, and aren't there other better aftermarket systems that do an even better job?

[JMortensen]

Zmanco, I tried to find an old thread that had hp numbers at different max timing settings and couldn't find it. It's been a couple years so it just must be buried in the database. My very vague memory says that someone lost upwards of 20 horses with a timing change of something like 5 degrees (might have been Norm???) Your timing setting sounds pretty close to me if you're using a stock distributor though, mid 30's to high 30's is usually what I expect to see for max timing.

[Daeron]

I suppose I left out a few details about my engine. I have 10.3:1 static CR and I have been driving around with that for a while. I had to retard the timing *slightly* to make sure I didn't blow head gaskets under heavy acceleration. Now that the cam is in the engine runs WAY better than it did on 10.3:1 and the stock computer, in the top end.

 

Oh yeah Z-YA... i have the little coolant fuel trimmer

 

Given this information, I am REALLY REALLY regretting opening this can of worms in this thread, heh TonyD reiterated my point best, it has to be suited for what it is in. IF it is suited, all I wanted to say is, it works perfectly fine. obviously in this guy's case standalone EFI is more than warranted.

[Tony D]

Yes, I have found 'going backwards' on the TPS and putting dual microswitches on like early VW, or even later BMW's makes for a nice adjustability, even on a STOCK car that is difficult to get running 'just right'... Hands down there are advantages to Standalones simply from what you can play around with...but then again there are some people who don't know what to leave alone...for those types I usually try to keep them into something that isn't adjustable, or needs a key to 'get to the good stuff'...

 

Some people would screw up Ice if they could! LOL

[z-ya]

I think think that saying the stock EFI is junk because of deteriorated connectors, or a bad AFM is not a fair statement. The same could be said about leaking carbs, with deteriorated gaskets, o-rings, bad floats, clogged jets etc. The stock EFI is a great system when in good working condition. Carbs also work great when in good condition.

 

Now when it comes to tuning, both have to be tuned. You can't just slap a carb on a modified engine, and expect it to run right. Same with the stock EFI. But as per my earlier post, you can tune the stock EFI to perform quite well on a MILDLY modified engine. There is no way that the stock EFI can make the power that a set of triples can, but you'd be surprised how much power you can make with a modified stock system. I've tuned a number of modified Z engines with stock EFI by faking out the ECU, and increasing the fuel pressure with very good results.

 

Megasquirt and other programmable units allow precise mixture adjustments at different load and RPM points. With carbs, you can only do so much with fuel and air jets. Most likely you can get the mixture right at full load, and max RPM. Anywhere else in the power band is a crap shoot. I've watched an expert changing air and fuel jets on a a set of Mikunis. Took close to 5 hours to get the mixture right at max RPM and load. It still had a super rich spot at 3000RPM. Not much you can do about that. With programmable EFI you can eliminate those flat spots.

[Tony D]

"I may be wrong, and I'm way out of my comfort zone talking specifics on FI systems, but isn't the stock FI limited by the restrictive AFM and manifold, batch fire, limited ability to adjust to different engine parameters (different cams, intake systems, etc) and no spark timing capability. Doesn't MS potentially get rid of all of these issues, and aren't there other better aftermarket systems that do an even better job?"

 

No, not really. A lot of it is internet myth or open to spirited debate. When people say EFI to me, I am thinking more on the Electronic End of it, and really the MS is basically the same as the stock system, you just have adjustability with ease. Sure it's MAP based, and you can drop your AFM...but where's the airflow numbers on the 'restrictiveness' of the stock AFM? It's like the argument over a bigger throttle body: the stock 50mm flows well more than enough to support airflow to well in excess of what the engine can pump at normally aspirated conditions. Batch Fire works, on both the stock system, AND MS. Sequential systems are over-rated IMO, and the 'advantages' are not to be seen except at the top end of motorsports competition. Idle is improved with sequential, but almost all systems switch over to batch fire over 3000 rpms---simplicity does have it's advantages.

 

In the early years, and even to this day, EFI systems are scrapped and given a bad name through technical ignorance! Technicians that are unwilling to learn a new system and coast on their job, it's more prevalent that you think! Simply stated, many times parts are swapped in a guess more than through any specialized troubleshooting. I'm no EFI genius by any stretch of the imagination, but knowing electronic theory is required for proper knowledge of the system, and many dealer mechanics simply aren't up to the task for whatever reason. And we all suffer (as does the system's reputation).

 

Spark timing capability in the stock system? Well by logical extension then Distributors are "Junk" or "Crap" as well, as they lack ease of maintenance or adjustability same as the stock EFI Box. My experience is that a fuel-only EFI system works just fine with a conventional distributor as long as your rpms are below 8000. It's a matter of need and want. Manyn people want what they really don't need.

 

As for the manifold, it is what it is...To blame or lump the electronics in with mechanical design gets a bit confusing. Sure it may be a restriction, but is that the fault of the EFI, or the costs involved in manufacture. I'm sure we all would have loved those 45MM ITB's from the 72 Rally Car and THAT JECS brain in our cars, or to even put it on in exchange for the commercial system used instead...but that goes to what the EFI was designed to do in the first place, now doesn't it?

 

The only advantage is easy adjustability. Now, if you swap in a Z31 ECU to your early Z-Car, and use Nisstune, you have almost the same EXACT tunability with a STOCK BOX that you do with the MS, or later standalones. Sure, there are some things you still can't really do, but this comes back to 'want' versus 'need'. In this regard, a STOCK Z31 EFI box could be considered "Superior" to a low-cost aftermarket system simply because it uses actual air-metering instrumentation, and will 'automatically' adjust for modifications. Such is the modern EFI that is MAF based. MAP systems may require adjustment after each modification as it changes things. Processor Speeds and capabilities keep expanding, with them more features become available....but at some point 'feature creep' just takes over, and people are marketed a bill of goods that they really don't need for the application! You don't need a full on Motec on a daily driver, or one even heavily modified. Conversely something with mild mods may work just fine with a fuel-only MS with the 8X8 tables and not even the 12X12! People get convinced they 'need' a 20X40 table for fuel...and then find a lot of the same setting in big blobs on the map... Hmmmm, maybe they didn't need all that resolution. Sure, resolution is great, and anybody that has looked at the GM code, you realize that the MAJORITY of the code is emissions compliance work-arounds for DRIVABILITY. Simply because they can quantify exactly where it occurs, digitally they can go RIGHT TO THAT SPOT and write a code for that specific situation. It may never get used... But you start stripping it away and you can find it really drives quite well 99.8% of the time without all that bloatcode.

 

Having worked in a Dealership and having to deal with "drivability" issues with Carburettors....they are no panacea. I have to agree with ZYa's last paragraph:

 

"Megasquirt and other programmable units allow precise mixture adjustments at different load and RPM points. With carbs, you can only do so much with fuel and air jets. Most likely you can get the mixture right at full load, and max RPM. Anywhere else in the power band is a crap shoot. I've watched an expert changing air and fuel jets on a a set of Mikunis. Took close to 5 hours to get the mixture right at max RPM and load. It still had a super rich spot at 3000RPM. Not much you can do about that. With programmable EFI you can eliminate those flat spots."

 

I'm not disagreeing about standalones superiority in many cases, but the stock box is not "Crap"... and that very same box conquered the world in Rally Competition running Triple 45mm ITB's...it was dyno tuned and set up to run the heavily cammed and fully competition prepped L24's in those cars. For an engine operating within it's designed parameters, IT WORKS! That is regardless if the car is stock, or was a World Beating Group 4 Rally Competitior with Triple ITBs! Matter of fact, the JECS system on that was a MAP Based setup more similar to the first generation VW setups...a more crude version but at that time had close to 10 years of durability testing and proven performance, so they deferred to 'reliability' versus 'best available technology' in that case.

[JMortensen]

Given this information, I am REALLY REALLY regretting opening this can of worms in this thread, heh TonyD reiterated my point best, it has to be suited for what it is in. IF it is suited, all I wanted to say is, it works perfectly fine. obviously in this guy's case standalone EFI is more than warranted.

Don't be so uptight! We're just arguing. Nothing wrong with that. I'm not taking it personally on my end, I hope nobody else is either.

 

Pete, you're right about the limited adjustability and tunability for carbs. Still when you're adding a cam one would think that the desire is to make more power, and with the limited adjustability of the carburetors it is still possible to make a bunch more power (and in this case a lot more across the entire rpm range) than with the stock FI.

 

Also the maintenance thing is a side track that I probably should have avoided, but Tony was touting the durability of the stock system, which I've always considered not very durable. But you're absolutely right, carbs or FI, it's going to require maintenance.

[JMortensen]

I'm not disagreeing about standalones superiority in many cases, but the stock box is not "Crap"... and that very same box conquered the world in Rally Competition running Triple 45mm ITB's...it was dyno tuned and set up to run the heavily cammed and fully competition prepped L24's in those cars. For an engine operating within it's designed parameters, IT WORKS!

I'm not saying what the ECU does is crap. I'm saying the ECU is crap. I'm saying the EFI system (mechanical and electrical, in this particular configuration) as used in the Z is crap when a person wants to modify the engine for power. The ECU may be able to be remapped for some crazy camshaft, but that doesn't mean that the stock FI from a 75 Z takes well to a bigger camshaft. Apparently this remapping of the computer isn't very easy compared to changing parameters on a programmable system. Since we are now in the 2000's and not the 1970's, that aspect of the ECU is "crappy". Again (3rd or 4th time now?), if your intent is to use it within its design parameters, then it can be made to function correctly. I have no argument for you there. But this is Hybrid Z, and the intent is almost never to use it within its design parameters.

 

EDIT--I was totally unaware that most FI systems revert to batch over 3000 rpm, but that does make sense in a way since the air is moving so fast that it probably doesn't make as much difference. Still spraying fuel on one closed intake valve and one that is right at the overlap point and another that is on the intake stroke all at the same time doesn't make much sense to me. It makes me think that TBI or even CIS would really be the way to go for top end performance.

[Daeron]

Don't be so uptight! We're just arguing. Nothing wrong with that. I'm not taking it personally on my end, I hope nobody else is either.

 

Not uptight.. just, a thread about a 10.3:1 compression motor with an aftermarket cam is a bad place to be the one sticking up for stock EFI on principle

 

Good to feel comfortable going "toe to toe" with you guys on a subject that, six months ago, would have been totally over my head though.. My brain hasn't been firing this well since my one year in college, and I LOVE IT!!!

[olie05]

Thanks to those who took the time to write novels for posts Seriously, the wisdom/opinions is appreciated and thats why this is the only forum I participate in!

 

So what I am hearing is:

 

I need a closed chamber head (knew that)

I should probably use a lower CR (knew that as well)

I need to switch to programmable EFI

I need to revise the stock timing map (duh thats the title of the thread)

 

and one thing I did not know is that porting the manifold will actually make a difference in performance without first porting the head.

 

JM, to answer your question, I was pinging under heavy load, and it caused a headgasket to fail. No, I am not running "several" head gaskets, rather I wanted to imply that I did not want to have to be replacing headgaskets in the future.

 

I have one week between summer session and fall semester... the plan is to become a social hermit and devote that entire week to:

 

1. porting my intake manifold to accept the 60mm TB and opening up the runners

2. installing megasquirt.

[z-ya]

Thanks to those who took the time to write novels for posts Seriously, the wisdom/opinions is appreciated and thats why this is the only forum I participate in!

 

So what I am hearing is:

 

I need a closed chamber head (knew that)

I should probably use a lower CR (knew that as well)

I need to switch to programmable EFI

I need to revise the stock timing map (duh thats the title of the thread)

 

and one thing I did not know is that porting the manifold will actually make a difference in performance without first porting the head.

 

JM, to answer your question, I was pinging under heavy load, and it caused a headgasket to fail. No, I am not running "several" head gaskets, rather I wanted to imply that I did not want to have to be replacing headgaskets in the future.

 

I have one week between summer session and fall semester... the plan is to become a social hermit and devote that entire week to:

 

1. porting my intake manifold to accept the 60mm TB and opening up the runners

2. installing megasquirt.

 

Give us more information on your setup.

 

Bore, pistons, head, etc. etc.

[Tony D]

I'll have to agree to disagree then. For the time frame it was produced, it was the most advanced system available and held up to the test of time as far a reliability goes---and there really was no alternative. People complain that plastic parts break after 30 years, I don't know what to do with that...sure the Europeans that bought BOSCH produced stuff got rubber that didn't deterioriate, and plastic clips with quick release bails (Volvo)....but look at what you paid for the stuff at the time compared with a 280Z! Everything is a tradeoff, if you wanted to pay another couple of grand for the car initially, you would most likely gotten stuff that didn't crumble to bits in 30 years. How many SU's were replaced from worn bushings at a couple of hundered thousand miles? The more complex something is, the more correct maintenance it requires. If you carry on status quo, even the most well designed system will get a bad reputation for unreliable operation! You can't make it idiot-proof, especially with the government breathing down your neck!

 

With the adjustability of the next generation of ECCS (available in the Z31) the stock box---simply because it IS reasonably adjustable really does negate most of the advantages of a standalone. The early box was not in an environment where the Prom needed reflashing. Today they are, BMW's with onboard celphones get new software downloaded form the maintenance center to attend to specific vehicle problems in production batches. The more features they add, the more complex everything gets, and the more the OEM's take propriatary ownership of the code and the servicing of the units. It's the only way they can keep their reputations intact. Unfortunately in the USA direct sales from manufacturers is forbidden, and thus there will always be pirates doing work that may or may not be in the best interest of the Manufacturer.

 

The system is really versatile, but it took almost 30 years for a reasonably priced alternative to become available. Sure, Carbs were there, but you were looking at well over a grand for them new...and like Z-ya said, they were far from 'easily adjustable'.

[BRAAP]

[Tony D]

[Daeron]

[BRAAP]

 

[Zmanco]

With regard to porting the intake manifold, is there something else that can be done besides matching it to the 60 mm TB and port matching to the head?

[Thumper]

2. installing megasquirt.

 

Have fun... umm yeah I guess if you have too call me if you need help:mrgreen: