[ananthkamath]

what is this TAP thing? Is it a microprocessor based device that lets you pull or add timing as a function of airflow/manifold pressure and RPM? If yes then huge gains can be realized with that kind of device. Compression ratio change may not be practical if the car needs to run on petrol at some point.

[ask77]

Originally Posted by Mpower

Has anybody tried increasing compression ratio in CNG/LPG cars to benefit from higher octane rating?

We got a wagonR DUO recently and I'd like to try this on my car.

Also would like to know if it has an in-built TAP or do I need one?

wagon r duo is a petrol/lpg dual fuel car . It operates on LPG not CNG . TAP is usually required for cng engines as the octane rating of cng is much higher at around 110 as compared to petrol's 87 so a timing advancer is very useful . lpg octane rating is around 100 so usually lpg retrofitters do not go for TAP . the latest technology for lpg is liquid phase injection system where liquid lpg is directly injected into the intake manifold of each cylinder much like a normal petrol car but with the additional advantage that the liquid lpg evaporates much more rapidly and cools the fuel/air mixture to make it much more dense and this could be used to increase the power output.
In theory cars with anti-knock sensors should be able to advance the timing on their own to make use of higher octane rating fuel can anybody throw some light on this aspect ?

[abhik]

Originally Posted by Mpower

Theres no need for pistons or conrods. All you need to pulll the cylinder head and get it machined and put back. Should be done within 2 grand.

I think the CR needs to be increased to about 16:1 or more like what diesels have and that cant be achieved by machining the head alone as i believe a normal NA petrol car runs 10:1 to 12:1 CR.

Originally Posted by ananthkamath

what is this TAP thing? Is it a microprocessor based device that lets you pull or add timing as a function of airflow/manifold pressure and RPM? If yes then huge gains can be realized with that kind of device. Compression ratio change may not be practical if the car needs to run on petrol at some point.

TAP-Timing Advancer is just an electronic device to advance timing in 3 stages of tune, timing cant be retarded only advanced with this device. It functions only when the vehicle is shifted to CNG mode else it is off on petrol mode. RPM, AFR, IAT etc are not regulated by this device.

[Mpower]

Originally Posted by abhik

I think the CR needs to be increased to about 16:1 or more like what diesels have and that cant be achieved by machining the head alone as i believe a normal NA petrol car runs 10:1 to 12:1 CR.

I seriously doubt there is enough valve clearance for you to go to 16:1. Diesels have a totally different type of cylinder head with vertical valves. Plus if you want to ever run in petrol mode, then it will be impossible.

Stock 1.6 is probably 9:1, so if you take it to 12:1 then it will show a great improvement.

Originally Posted by ask77

wagon r duo is a petrol/lpg dual fuel car . It operates on LPG not CNG . TAP is usually required for cng engines as the octane rating of cng is much higher at around 110 as compared to petrol's 87 so a timing advancer is very useful . lpg octane rating is around 100 so usually lpg retrofitters do not go for TAP

yes, I am aware of that, but I'll take what ever improvement I can get at 12:1

[Gangsta]

Originally Posted by abhik

TAP-Timing Advancer is just an electronic device to advance timing in 3 stages of tune, timing cant be retarded only advanced with this device. It functions only when the vehicle is shifted to CNG mode else it is off on petrol mode. RPM, AFR, IAT etc are not regulated by this device.

i don't know at what stage TAP is installed in my car. is there any way to find it out myself?

[abhik]

Originally Posted by Gangsta

i don't know at what stage TAP is installed in my car. is there any way to find it out myself?

I am Guessing the fitter would have wrapped the TAP in plastic sheet to save it from water and moisture so unwrap it and disconnect it from the socket it was plugged into. On that very end you will see a little red LED on the left hand side and 3 switches, two or one of which should be facing upwards(depending upon the way you are holding that box). This will indicate at what setting the timing has been advanced. Usually the 3rd setting is not recommended as the timing advanced at that setting will make the engine go bezirk but would eventually harm the engine!
Just check the box for curiosity's sake but dont fiddle around with it, it would be better to ask the fitter about the settings your car's engine is supposed to have. Remember to wrap the box in plastic again before reinstalling the box.

[abhik]

Originally Posted by Mpower

I seriously doubt there is enough valve clearance for you to go to 16:1. Diesels have a totally different type of cylinder head with vertical valves. Plus if you want to ever run in petrol mode, then it will be impossible.

I know, and that why i mentioned that untill we can lay our hands on engines specifically built for CNG, it will just be sort of running around the tree when you need to reach the top.
I am sure you know that diesel engines are made stronger than their petrol counterparts thus running 16:1 CR would be next to impossible anyways and even if you do then you could probably forget running the car on petrol and besides the ever lingering fear of a breakdown becaused of internal failure due to the stress on the internals.

Originally Posted by Mpower

Stock 1.6 is probably 9:1, so if you take it to 12:1 then it will show a great improvement.

But then we are loosing the whole point arn't we.
We put CNG/LPG in our cars for economy even after the huge initial investment, and the modding the vehicle for performance on CNG/LPG. I have walked these roads for the past year and a half only to realise how stupid i was.
To admit a few realities:-
1. After CNG/LPG installation one never feels like switching over to petrol even if you know you want to do tripple digit speeds and petrol will anyday be better at doing this job.
This hampers the engine as running on CNG raises the engine operating temperature and thus overall efficiency(in terms of engine performance not FE) goes down. Simple rule of thumb-cooler engine = better performance.
Higher heat means more wear and tear of the internals, stock spark plugs enhances this effect and colder heat range plugs are needed for CNG, engine oil runs hotter which inturn again reduces its efficiency of protecting the engine as it loses its lubricating properties.
2. Raising CR- Good for CNG, but when you have to run the engine on petrol the FE figures that the engine will return will not only make you lose the smile on your face but also a lot of cash from your pockets.
Also FE on CNG will also reduce which beats the whole piont of installing it because we did so for economy, agreed that price of CNG is nothing but its such a headache to stand in long queues to fill up for just 9-10kgs which due to mods will run out even faster, thus trips to the station increase and so does the time required for the fill up. Dedicating 2-3 hours for a couple of fill ups in a day does not make sense to me.
3. CNG is meant for 50-60kmph driving in traffic and a switch over to petrol when you want performance and high speed driving but how many of us do that. Atleast i did'nt.

I remember a day when i had to pick up my cousin at 12 noon and i was already running late because i woke up late, only to realise i had no CNG and no Petrol since i had to go to Greater Noida which is approx 45kms from south delhi where i stay. Even after knowing that somebody i waiting for me i still went so fill up CNG looking at the fact that petrol would have costed me Rs325 oneway(7kmpl with A/C on my Ikon with hard driving and petrol at the time was at Rs50.XX in Delhi. so about 6.5liters of petrol. Roundtrip would be Rs650.) It took me 1hr30mins to fill up and head out and i reached there 3hrs after the scheduled time.
CNG just costed me about Rs.160 for the whole trip with A/C.
This is what CNG made me- miser.
Now that i think of that incident, i so so hate myself. I was willing to make my cousin wait, drench myself in sweat while waiting for my turn at the CNG station(remember no CNG very very little petrol so no A/C), hate being late for anything but still did'nt bother at that time.....all for what just Rs.490, i earn well to give up that amount and not let my cousin wait 3Hrs. Nevermind...

Besides this the other reasons have already been mentioned by me which are technically related to the engine and how it over a period deterioted the performance in my Ikon as CNG is definately not suited for my driving style which is fast and aggressive( i manage to do this safely aswell as i am very particular about safety-my own and others on the road.)

For me the best bet was a performance diesel or a good FE petrol car and thats why i sold the Ikon for an OHC-good mix of performance, reliability, low cost of maintenence and good FE. No CNG for the OHC.

[saintsinner]

so, CNG guys - CAI on a CNG vehicle is no good?

A question here, the CNG mixture that is attached to the throttle body, it has a smaller bore. it is 25mm and the throttle body is 54mm (accent). now i presume that is because you want to let lesser air inside. what if a custom one is machined of the same size as the throttle body.

Arush, please comment on the CAI for CNG cars.

[saintsinner]

Post deleted by the Team-BHP Support : Please do NOT SPAM the forum. One-liners that add absolutely no value to the thread are strictly prohibited on Team-BHP.

We advise you to visit our board rules section before proceeding any further.

[ask77]

Originally Posted by saintsinner

so, CNG guys - CAI on a CNG vehicle is no good?

A question here, the CNG mixture that is attached to the throttle body, it has a smaller bore. it is 25mm and the throttle body is 54mm (accent). now i presume that is because you want to let lesser air inside. what if a custom one is machined of the same size as the throttle body.

Arush, please comment on the CAI for CNG cars.

The mixture that is attached to the throttle body is narrow because it creates a venturi effect like the carb in older cars to suck in the gas and is calibrated for that purpose . The gas comes in 'on demand' ie. as the intake air rushes thru the mixture venturi it creates a vaccum the degree of which is determined by the volume of air and that in turn sucks in gas accordingly to create the proper fuel/air ratio. So in my opinion the mixture is a critical component of a gas kit and its design plays a important role in the operation of the system. How much the design can be played around with to get a better performance is a question to be answered by experts.

[abhik]

Guys, an engine run on CNG needs to run cold and what best than giving it COLD intake air but a Typhoon or Apollo kit by K n N wont really solve the problem. The CAI has to be routed such that it gets maximum air from outside(at ambient temperature) and minimum hot air from around the engine bay. Cold air is also necessary for more oxygen which is required to efficiently combust CNG as it is a higher octane fuel.

I have also ventured into making a custom mixture with a larger venturi for more air intake into the engine but all that will do is make your engine incapable of running on CNG. The mixture is made on calculated geometry keeping in mind the size or capacity or displacement of the engine. With CNG the AFR has to be very precise and that only a certain amount of fuel(CNG) can be mixed with a certain amount of air only for good combution without knocking, if any of the components are increased or decreased then the result is the engine refusing to start or if it does it will stall at lower RPMs. Unlike petrol engines where the AFR has a wider ratio to run lean or rich, CNG as compared has very little margin with regards to running lean or rich mixtures. So a free-flow air filter will not really be helpful but a CAI would be. Thats why a Sequential Injection kit is recommended as the ECU(piggyback) which comes along with the kit has one of its major functions of deciding AFR on CNG than Lamda on a regular kit.

[panky12345]

hi, never wanted to open a new thread so posting it here.

I'm using a Tata Xeta 1.2 with CNG..recently i discovered with A/c ON car jerks badly around 2500 RPM in any gear, particularly while accelerating it.
Am I stressing the poor engine too much? CNG and then A/c? For the sake of info, my car uses a BRC sequential kit.

any inputs?

sorry for the double post.. requesting mods to delete from unappropriate thread!

[panky12345]

Bump: NO clues people??

[ashthedivx]

May be you need to lookout for a cleaner air filter and cleaner throttle body !! Indica had some niggling issues with CNG but not that much that you'll feel jerking @ > 2500 RPMs.

May be you need to open up CNG valve a bit more, it might be tuned for extra mileage rather then extra power.

[panky12345]

Originally Posted by ashthedivx

May be you need to lookout for a cleaner air filter and cleaner throttle body !! Indica had some niggling issues with CNG but not that much that you'll feel jerking @ > 2500 RPMs.

May be you need to open up CNG valve a bit more, it might be tuned for extra mileage rather then extra power.

Got the air filter cleaned recently..

the jerking happens when I try to accelerate at a faster pace than usual.. if I do it gradually, then it's not a problem.

any pointers?