Ola`s jimny project

My m16 VVT had sadly no change in power after removing a broken cat element from the exhaust manifold. I was expecting some difference especially when the element inside the cat had broken and the broken pieces was lying across and partly blocking the flow. It looked like it was obstructing at least half of the cat so I think it was strange that i almost did not feel any difference when i removed it completely.
the flow in the intake and TB, and thru the exhaust are balanced and made to fit to make sure the air and fuel mix is optimal. Changing only one item like the TB is often not any help as putting a wider TB there will slow down the air thru it in most cases.
Bad air/fuel mix can also make ingition pinging?

When we change from 1300 to 1600 there is almost 20% more air that should be going thru it?
If we do not change the diameter then it will have to flow faster and bends and obstructions will have more significance to the optimal flow.
The cylinder head will probably play the largest part in this.
The lack of high end power suggests that the flow is really the problem and when removing the cat has little effect i think the intake is the place to try to do something in my case..

I dont think it`s only one of the sides that has to be improved, as both affect each other..
If the exhaust doesent help evacuate the gas/heat, the next stroke will be less effective.. If the intake is to small/bad flow, the exhaust will not be flowing well out of the cyl, and there will be less fill of new oxygen/fuelin the cyl on next stroke..
Even worse on the more agressive cams in the SS motor i reckon.

I`m thinking M18a intake/throttlebody + full exhaust, that should do it.

I am planning to run throttle bodies (danST) and a 421 header with a 2" 200 cell CAT and straight thru system. ME221 ecu to sort the fuelling as the VVT denso can't be overwritten easily.

These are going on a 1.3 vvt, the existing induction and exhaust system are massively restricted, I'm hoping to get 1hp - 1cc, it will take cams and headwork to get there but I think the little lump is ace

Existing tb is 46mm for four ports, these will give 38mm to each port and in a straight line.

The exhaust is is even worse, manifold/front cat is horrid and prone to collapse and restrict. The system is poor.

An improvement in air flow through the engine will to a certain extent be managed by the existing fuelling system but it could loose power because it can't now be timed and fuelled to an optimum. Adjustments to ignition timing and fuelling, mapped live under load, is the only way to restore "balance" and get the improvements that the changes have the potential to deliver.

Very few of us would want to drive an engine that is tuned purely for peak power, I spent a year driving a classic mini with stage 4 head 310 cam and a weber 45, 107bhp at the wheels. Every set of lights was a nightmare, you needed 4000rpm just to slip the clutch and then you launched it.
It looked like you were racing from every stop start. Only ever sounded right at half throttle or more, peaky - lumpy just generally not nice.

A 4x4 wants a broad spread of power across as much of the rev range as possible.

You can only manipulate the power/torque curves on an EFI engine thru the ecu. The standard ecu does an amazing job, I've seen 1.3, 1.5, 1.6 and 1.8 running on it thru these pages, bloody amazing....... but if you can't overwrite it for a tune that suits the specific modifications, you loose in many ways.

The 1.6 vvt will respond well to exhaust and induction mods BUT you've got to be able to programme the fuelling and ignition. Over 200bhp is often seen in swift rally cars, I would guess that somewhere around 150-160 should be available without head mods or cams

It's a package deal in my opinion, you get some benefit from improvements to induction and exhaust but they will only give their true potential if mapped correctly. So fitting an after market ecu will probably be necessary to release the engines potential.

Great thread.

sniper

sniper wrote: I am planning to run throttle bodies (danST) and a 421 header with a 2" 200 cell CAT and straight thru system. ME221 ecu to sort the fuelling as the VVT denso can't be overwritten easily.

These are going on a 1.3 vvt, the existing induction and exhaust system are massively restricted, I'm hoping to get 1hp - 1cc, it will take cams and headwork to get there but I think the little lump is ace

Existing tb is 46mm for four ports, these will give 38mm to each port and in a straight line.

The exhaust is is even worse, manifold/front cat is horrid and prone to collapse and restrict. The system is poor.

An improvement in air flow through the engine will to a certain extent be managed by the existing fuelling system but it could loose power because it can't now be timed and fuelled to an optimum. Adjustments to ignition timing and fuelling, mapped live under load, is the only way to restore "balance" and get the improvements that the changes have the potential to deliver.

Very few of us would want to drive an engine that is tuned purely for peak power, I spent a year driving a classic mini with stage 4 head 310 cam and a weber 45, 107bhp at the wheels. Every set of lights was a nightmare, you needed 4000rpm just to slip the clutch and then you launched it.
It looked like you were racing from every stop start. Only ever sounded right at half throttle or more, peaky - lumpy just generally not nice.

A 4x4 wants a broad spread of power across as much of the rev range as possible.

You can only manipulate the power/torque curves on an EFI engine thru the ecu. The standard ecu does an amazing job, I've seen 1.3, 1.5, 1.6 and 1.8 running on it thru these pages, bloody amazing....... but if you can't overwrite it for a tune that suits the modifications, you lose power and drivability.

The 1.6 vvt will respond well to exhaust and induction mods BUT you've got to be able to programme the fuelling and ignition.

It's a package deal in my opinion, you get some benefit from improvements to induction and exhaust but they will only give their true potential if mapped correctly. So fitting an after market ecu will probably be necessary to release the engines potential.

Great thread.

sniper

I agree on pretty much all of youre post

I am going for a dyno tune, maybe in a months time.. Just want to be "finished" mechanically first, as its expensive to dynotune.
They claim they can fully tune my stock ECU, so that should be the best solution for me and my setup.
I want more top end ofcourse, but just as important is to tune the low end for it to handle low rpm situations better (which now is alot better allready than on the 1.3).

You`re setup with ITB, needs a standalone i think, mostly due to the loss of common map sensor? I think you need to map against the throttle angle sensor and not map sensor (both can use MAF sensor ofcourse, but i suspect you plan to run without a collector intake in front of youre ITB`s?).
You will get alot more throttle response, but also alot less resolution in youre low throttle positions.. This i do not like for a offroad car.. But it`s possible to get some of it back, if you use a completly different profile on the throttle cable gear, to slow down the movement alot in the low end.

Breather kit installed on both axles..
Gear box allready has this from stock, but i`m going to do the transfer also , when i pull it out for re-gearing. No room for doing it in the car.

Front


Rear.. Dont like the "water trap" though, might be running it individually straight up to the rear of the car instead to avoid this, if it shows to trap condense water over time.

Yes it will be a bit peaky at low throttle but I have some experience of tuning the induction length with trumpets pre-butterfly. Geared linkage may also assist, done it on a twin IDF set up before but I hadn't considered it for this job.

I think it will make much more use of low range than it does now, but as you say, it will spin up like a rocket. That will be a negative that I hope to be able to tune out, possibly having a two stage tune, one tarmac the other for low range.

I will ask the supplier if he has ever had reason to dampen throttle response and see where we go.

Thanks for the nod, I probably wouldn't of considered it as an issue until I'd buried my wheels........

sniper
(just had a look at some S1600 rally engines and CTC have 178bhp@8750rpm, albeit with forged internals but it shows the engines got plenty of potential)