4AG w/TVIS engine mods

[BroBri]

Hi All,
Beginner here, so please bear with me.
If I slap some cams in my 4AG to get a bigger valve lift, do I need to modify the pistons to accommodate the extra lift?
And if I shaved the head a bit, same question?
Thanks,
Brian

[yoshimitsuspeed]

Hi All,
Beginner here, so please bear with me.
If I slap some cams in my 4AG to get a bigger valve lift, do I need to modify the pistons to accommodate the extra lift?
And if I shaved the head a bit, same question?
Thanks,
Brian

The 16 valve is a non enterferance engine so you have enough room that you really don't have to worry about hitting the pistons due to lift but it doesn't take much cam to make it an interference engine.
If you add cams it's ideal to add as much compression as possible to compliment them.
Personally I wouldn't waste time trying to shave the head to get the compression up on the stock pistons. I can get oversized Supertech 11:1 pistons with rings for around $450. This allows you to bore the block and gain your compression without shaving the head.
If you are looking for moderate gains with a broad power curve and stock redline these are by far my biggest selling cams and the reports back on them are always positive.
http://matrixgarage.com/products/tomei- ... 64-81mm-ex

[apsogosGTi]

i have an ae92 corolla hatch.It is the 2nd tvis version european specs with 10.1 pistons and rebuilded with shaved head about 3/10 of a milimeter (if i am writing it right)
These cams can play on my setup?

[yoshimitsuspeed]

i have an ae92 corolla hatch.It is the 2nd tvis version european specs with 10.1 pistons and rebuilded with shaved head about 3/10 of a milimeter (if i am writing it right)
These cams can play on my setup?

The poncams should work great with your motor. If you have a non O2 ECU I don't know for sure how it will like them. It will probably run fine but may be optimized by tweaking the AFRs. A wideband would probably be a very helpful tool.
Of course the same goes with the O2 ECU. It runs well with the cams but can be dialed in better with a wideband.

I just setup a discounted group buy for poncams if anyone's interested.
viewtopic.php?f=22&t=9454

[apsogosGTi]

i have an ae92 corolla hatch.It is the 2nd tvis version european specs with 10.1 pistons and rebuilded with shaved head about 3/10 of a milimeter (if i am writing it right)
These cams can play on my setup?

The poncams should work great with your motor. If you have a non O2 ECU I don't know for sure how it will like them. It will probably run fine but may be optimized by tweaking the AFRs. A wideband would probably be a very helpful tool.
Of course the same goes with the O2 ECU. It runs well with the cams but can be dialed in better with a wideband.

I just setup a discounted group buy for poncams if anyone's interested.
viewtopic.php?f=22&t=9454

i have no o2 sensor and no catalytic converter!

[yoshimitsuspeed]

i have no o2 sensor and no catalytic converter!

You do have an AFM though right? AFM cars handle VE changes much better than MAP cars.
I think your ECU would handle them just fine but I would get a wideband just so you could monitor and fine tune it.
No cat is not going to be any issue.

[gotzoom?]

I have almost exactly what you are proposing and it works well. I'm currently running the smallport high compression pistons with a largeport head, TVIS and Poncams on the stock USDM ecu.. The idle is slightly lumpy and I had to raise the idle a little higher (maybe 1/2 turn higher) to keep it running, but no other changes were required. I did have to move to 89 octane fuel though. I get pretty bad ping if I run 87 octane. If you've got a tank of 87 in the car now, you may want to have a bottle of octane booster at the ready.

[yoshimitsuspeed]

I have almost exactly what you are proposing and it works well. I'm currently running the smallport high compression pistons with a largeport head, TVIS and Poncams on the stock USDM ecu.. The idle is slightly lumpy and I had to raise the idle a little higher (maybe 1/2 turn higher) to keep it running, but no other changes were required. I did have to move to 89 octane fuel though. I get pretty bad ping if I run 87 octane. If you've got a tank of 87 in the car now, you may want to have a bottle of octane booster at the ready.

But the USDM ECU uses the O2 sensor to fine tune the fuel trim. This means that it can compensate for rather large changes such as VE or Altitude or even a little boost. The non O2 ECUs have a manual adjustment to dial that in. Like I said it may adapt to it fine but unless he can find someone who has monitored AFRs on the same ECU and cams personally I wouldn't do it without a way to monitor them myself.

Also bigger cams make detonation less likely so if you aren't getting it before putting in cams then you won't have it after putting in cams. If you do then something is wrong.
My customer running 11:1 compression and poncams gets a little detonation in the mid RPM but it's not audible without a detcan. He also isn't running his EGR and right where he hears it is right where the EGR should be functioning.

[apsogosGTi]

No i havent afm.My engine is map sensor equipped!

[allencr]

My customer running 11:1 compression and poncams gets a little detonation in the mid RPM but it's not audible without a detcan.

What is midRPM and where abouts is the static/idle & max-advance ignition timing set/come-in at and what is a detcan & what is it connected to and isn't WOT under 3000rpm just abuse?
Thanks.

[yoshimitsuspeed]

No i havent afm.My engine is map sensor equipped!

My bad I thought that model was AFM. Or maybe there was a similar model that was.

I would love to hear from someone who has tried this on your setup but without it I can only hypothesize. People don't have any trouble dropping cams into the MAP based Blacktop so that is a good sign but the BT still has the O2 to fine tune fuel.
With a wideband I suspect you could get them working well enough but I just don't have enough familiarity with that setup to tell you for sure.

[yoshimitsuspeed]

My customer running 11:1 compression and poncams gets a little detonation in the mid RPM but it's not audible without a detcan.

What is midRPM and where abouts is the static/idle & max-advance ignition timing set/come-in at and what is a detcan & what is it connected to and isn't WOT under 3000rpm just abuse?
Thanks.

If you want details you can browse through this thread.
http://www.mr2oc.com/showthread.php?t=468649

If I remember right it was mostly around 3500 to 4000 RPM and I believe was actually worse at partial throttle. This is actually very common with detonation and makes sense. At partial throttle the engine is still running at stoich in closed loop. WOT will throw more fuel at it making it run richer and cooler. Partial throttle is also when the EGR is supposed to be open and circulating. This makes the motor much less likely to knock. It's theorized that any EGR equipped ECU will throw more timing advance in this range to take advantage of the decreased chance of detonation from the EGR. Remove the EGR and it will be more likely to knock in that area.

[BroBri]

Thank you yoshimitsuspeed for the info.
When you talk about the Supertech oversized pistons, what exactly do you mean?
Are they longer on top, thereby creating a smaller cylinder volume when they are at bottom of stroke?
Please excuse my possibly stupid questions as I am new to engine work
I race on an asphalt circle track, and the rules for my class only allow .04" overbore from stock, and a max compression of 12:1.
Can you tell me the max valve lift before I need to rework pistons to prevent interference?
From what I can see on Bill Sherwood's page, standard 4AG cams are 240 degrees duration and 7.56mm (.298") lift.
I also see that a 264 degree duration is the limit for the stock ECU.
If I dropped a pair of your cams in, would I need to modify pistons?
Would I see a big difference in power?
Thanks for your help,
Brian

[oldeskewltoy]

Hi All,
Beginner here, so please bear with me.
If I slap some cams in my 4AG to get a bigger valve lift, do I need to modify the pistons to accommodate the extra lift?
And if I shaved the head a bit, same question?
Thanks,
Brian

slapping in cams... you can lose power by incorrectly installing cams. All camshafts installed in any engine should be checked for cam timing... recently I checked cam timing on a friends engine and if we hadn't checked the cam timing, the camshafts would have been mis-installed by 15 degrees!




a lot of lift isn't going to help a great deal since most of the 16V 4AG heads go flat (flow volume) at between 7mm and 7.5mm lift - see below redline is stock 4ag exhaust port, green is ported exhaust port, blue is stock 16V intake , while yellow is ported. The tiny arrows indicate the lift maximums of the stock camshafts red is 232 duration 1988+, while the blue arrow represents the earlier pre-1988 camshafts



Even a mildly ported head still shows flow improvement well beyond a stock heads ability to flow.

[yoshimitsuspeed]

Thank you yoshimitsuspeed for the info.
When you talk about the Supertech oversized pistons, what exactly do you mean?
Are they longer on top, thereby creating a smaller cylinder volume when they are at bottom of stroke?

Technically yes but it's at the top of the stroke you are concerned with. The bore and the stroke sets the displacement so that doesn't change.
The piston fills more area in the combustion chamber so it compresses the air more creating a more powerful combustion. At a point that compression can be so high it can cause preignition or detonation.

I race on an asphalt circle track, and the rules for my class only allow .04" overbore from stock, and a max compression of 12:1

.04" is a little over 1mm so you could run their .5mm over or 1mm over. Starting with the .5mm over means you could bore the block one more time and step up to the 1mm over in the future. If you went with the 1mm over you would need to get a new block if you wore out the bores.
The supertechs should be a good option but if you are serious about being competitive I would probably go with a custom piston designed specifically for your application and max compression. I can get custom Wisecos made for about $100 more than the supertech pistons and they will give you a notable edge. I can also get customs from CP or JE if you prefer but the cost is slightly higher.

Can you tell me the max valve lift before I need to rework pistons to prevent interference?

On the stock pistons I cannot.
I could find out on the Supertech 18mm. The 20mm wristpin pistons will actually be non interference with the poncams so you could throw a ton of cam at them without worrying about hitting. I did this because I wanted a high performance alternative to the OEM pistons. Something that would be stronger, higher compression and better than stock in every way while staying non interference with my biggest selling cam. This piston is for daily drivers and mild builds that want good performance for a long time. They are not optimized for max performance.
The great thing about going with a custom piston is you can design it specifically around the cams you plan to use. You can minimize valve reliefs and dome making the flattest piston possible. This reduces sharp edged and complex contours that can lead to preignition, detonation or an uneven burn. If you think you may want to run a little more cam down the road then we can plan for that to give you a little room for changes.
It's also at this point that you want to decide if you want to run bigger valves or anything like that since you will need to plan it into the design.
In a situation like yours it really comes down to two things. What are you allowed to do and what can you afford to do.

I also see that a 264 degree duration is the limit for the stock ECU.

Limit is really a misnomer. The NA ECU has been boosted to over 150 WHP. If it can fuel for that much air on boost than it can fuel for that much air on cams.
The problem is that bigger cams move the power up in the rev range and at a point your peak power will be above the stock redline. The ECU can still run the motor fine but with the stock rev limit you won't be able to access the power above redline.
There is also the issue that lift is only one part of the equation. As OST pointed out at one point the poncams with 264 deg total duration have 222 deg duration at .05" whereas the Web 101 with 250 deg total duration cams have 229 deg lift at .050 so the poncams total duration is significantly higher but the web cams are just slightly higher in the range that is really important. If WEB made a 264 rated cam with a similar profile and proportionally increased lift it would act like a much bigger cam than the 264 poncam.

For a racing motor I think a litttle bigger than the poncam could be advantageous. Even if you can't take advantage of all the power on the stock ECU you should still be able to get at least the same powerband as the poncams under the max rev limit. If you decide to go to aftermarket engine management then you would have even more available to you.
I would really like to see what this cam can do.
http://www.camshaftshop.com/products.ph ... =818#specs
I don't have it on my website but I can get a pretty decent price on it.
I think that cam with 12:1 compression would be pretty impressive across the rev range.

If I dropped a pair of your cams in, would I need to modify pistons?

You wouldn't need to but you would want to.
Bigger cams gain you more high end power but sacrifice low end. Low end is also where detonation is the most likely so a bigger cam means you can run more compression. If you balance this right you can have as much or more power in the low end while gaining a lot of power in the high end.

Here is a dyno that shows what I mean.

You can see that the poncam with stock pistons looses just a little power under 4000 RPM.
On the other hand the camshaft plus high comp pistons maintains the higher power up till 4k same as the smaller cams but after 4k the power is well above both other dynos.
If you want to maximize the performance of a motor you want to design the cams and pistons around each other.
The power loss under 4k isn't very big on the poncams but the bigger the cam you run the bigger that loss will be unless you make up for it with compression.

Would I see a big difference in power?

You can see the differences with the poncams on the dyno above.
Here is another example.

Here is a stock 4A AW11 dyno.



VS 11:1 compression and poncams.


His car wasn't very well tuned on this run and he is quite confident he has picked up a noticeable bit more power just with some tweaks with the stock electronics.
Add some well done Port n Polish work and there should be a bit more to be gained.
Personally I am a big fan of boost. Bang for the buck it's hard to beat. When it comes to real racing though you are limited by the rules of your class and in that case the rules are much different.

[BroBri]

Thank you yoshimitsuspeed for all the great info.
Will "chew on" this for a while and save some money up.
Gotta' finish disassy on the engine and clean up the block, then start getting parts to reassemble.
Thank you also to oldeskewltoy for the good info.

Brian

[BroBri]

yoshimitsuspeed- can I get an email address to correspond with you direct?
Have some more questions also.
Thanks,
Brian

[yoshimitsuspeed]

yoshimitsuspeed- can I get an email address to correspond with you direct?
Have some more questions also.
Thanks,
Brian

http://www.matrixgarage.com/?q=content/contact-us