Sunday, November 28, 2010

4G93 Modification From Mild to Extreme

For those 4G93 engine (first generation) owners who wish to modify their engine to on path with the Honda B18C, let's continue to read this post. All these information of this post were gathered from the net. Thus, I would like to thank all the author of these informative articles.

In any engine, the only way to make more power is by adding more air and fuel. This is why Turbocharger and Supercharger came in mind in the early decade. For Normally Aspirated (NA), we can try to increase the breathing performance and efficiency. There are several ways to increase the breathing efficiency and here are some of those things that help to improve the performance of the engine.

1. Increase the port shape and size so that more air flows in without losing the velocity.

2. Increase the cam duration and lift. The longer the valves are opened and lifted the more the air can flow in. However for a NA engine, the bigger cam duration and lifts are still depends on the vacuum to suck the air in and this area is compromise.

Having the ports open sooner and more valve lift is the equivalent to increasing the air and the engine will lose the velocity. However, this problem is not an issue once there's an increase in revs and the efficiency of the engine is enough to match the camshaft characteristics.

There are many ways to open and close the cams and most road engines usually use a mechanism called a hydraulic lifter or followers. The advantage of this mechanism is its quiet and doesn't need frequent and labor intensive adjustment like a solid lifter engine. However, there is a downside to the hydraulic lifter where it can't have a long duration and lift.

Let's talk about how to modify the 4G93. Here are some of the things you may do:-

1. Increase the compression ratio of the engine.
- When using a bigger cam profiles, normally we will lose the dynamic compression. But as we know that the theory shows that every 1 point of compression increase in the engine, there will be approximately 3 or 4% increase in performance. So by increase the compression ratio to 11:1 according to Honda VTEC B series engine specification or the 11.5:1 of the Toyota VVTL-i engine, we can gain an impression increase of performance for the 4G93. FYI, the compression ratio of 4G93 is around10:1.

2. Good port shapes and flow of the engine.
- The B18C straight out of the box flows an amazing 141+ cfm with no loss when the throttle body and inlet manifold are fitted compared to the 4G93 at around 120+cfm. As long as you able to find a mechanic with good knowledge, skill and experience of porting the engine, there will not be a problem of losing the velocity.

3. Increase cam duration and lift.
- A stock 4G93 is having approximately 256 degree and at 8++mm of lift. Try to change the cam to mild cam (288 degree) and with an inlet valve lift at 11.5mm and 10.5mm for exhaust valve. This is just a reference from me because mild cam is more daily driving friendly. If you wish to have a higher cam profile, you may try to increase to 300++ degree but bare in mind that you will suffer bad idling at lower rpm. 

For first generation 4G91 and 4G92 (non MIVEC) engines owners who wish to maintain NA path and modify their engines to on path with Honda B series engines, you may have this information as reference. 


Although I'm a 20V user, I always look forward to your 4G tuning posts. Keep it up!
P/S: write similar posts about modding 20v blacktop also hehe

Thanks a lot ePuL. I will try to post some similar modding info about 20v in the near future. Do stay tuned.

Any idea what is the piping size for 4G93 exhaust?


Depends on what modifications you had done to your car. Normally people will change to 2.3" piping size.

Hi bro,
Just came across ur blog.Very interesting n informative.Planning to swap my 4g15 to 4g93. wat r the necessary things important to look into?ur advice is highly appreciated.

Hi Dinesh,

I assume that you are getting the entire halfcut. First thing you need to do is to start the engine and check for the oil leakage of the engine. Second, do get a set of rear disc brake since 4G15 does not have any. If your car equipped with a carbie engine, get the EFi fuel tank as well (basically come with the halfcut). Last but not least, remember to get the custom form and the receipt of your engine in order for you to register it legally.


Hi Ben,

a question for u. today my foreman say 4g93 is very difficult to transplant to my wira because of its wiring layout which is different from that of 4g15's. is it true?


hi bro...just want a clarification from u..
i just bought a tomei camshaft (290 11.1)..
but the packaging is not d same with yours..mine written tomei poncam procam..i just curious bout its originality..

Hi Dinesh,

Yes both wiring are different. But as long as you buy halfcut, you need not to worry about wiring before you will convert everything from the halfcut to your wira.



If not mistaken, it is the new and old packaging different.


Is this applicable to the SOHC 4G93?

Hi Dean,

Yes, this is applicable for SOHC as well.

hi ben,u answered dean that this applicable to 4g93 sohc..what bout 4g92p(sohc)?im owning 97' satria xli..bought 2nd hnd n previous owner already chnge whole exhaust system (4-2-1 and twin muffler like gti)and some cheapo open pod,plus cable plug sipeco 9.8mm..wonder what needed to be throw away and put in?

Hi Qaiyim,

May I know what is the size for the exhaust piping? If the size is not suitable for 4G92, it is recommended to install a suitable piping size to your 4G92. Change to a better open pod and a CAI to direct cold air from outside. Besides that, change a set of better spark plug to couple with your plug cable.


size?i'll chck later..yup,already looking for iridium..but wht type?brand is suitable?thnk u ben..u r vry helpful~

hi ben...after change to 2.3" piping will it eat more petrol?? mine is SOHC, wit oly 1.8" piping rm50 can oly run 200km..==""" and i didnt mod anything yet.. jus have a FICD for aircond, HKS filter..


Fuel consumption will depends on your mod. I can't give you a exact fuel consumption level of your car. Probably there are some other things that affect your car FC. For eg: plug cable, spark plug and etc.


hai bro,

what is the best size of exhaust for 4g93 na without any mod. just to get your view, what should i do first to mod my car? change the exhaust or the parts as u mention above? thanks

The best size is 2". Change the exhaust and the intake system first. Then only change the parts as mentioned above.


Hi Ben,

Currently i'm using 4g93 from Putra. I want to change my gearbox and there are several gearbox option I found: gsr 4wd(lock), gsr 2wd, satria GTi gbx..which is the best for my current engine?

Hi Own,

GSR 2WD or GTi suits you the best.


hi ben,

now i'm using 4g15 mitsu carb engine after change from original 4g13. 4g15 with piper cam etc.good respond compare to stock esp when use 32/36 weber carb.but problem occured n now use back original plan to use 4g93 sohc carb engine with gearbox 4.7 ratio and twin dcoe40 weber. my question are:
1) can use existing engine mounting?
2) drive shaft-change to 4g93 or can use 4g15 d/shaft?
3)need to modiify wiring?now i'm using evo3 dahsboard
4) what do thick in term of fuel consumption?


Hi Syam,

1. Can use back engine mounting since it is plug and play for 4G series engine to Proton older model.
2. Change to 4G93.
3. Since it is carb, don't think much of wiring needed for your conversion. Just minor like those signal and etc.
4. Thick?


Hi Ben,

sorry..question no.4..wrong typing.actually my question..what do you think in term of fuel consumption if using twin carb dcoe40..another question to u:
1) i plan to change crankshaft 4g93 to 4g94 to get 2.0cc..what piston, conrod and thickness of metal gasket?
2) is it possible to convert sohc to dohc but still using twin carb dcoe?
3) is it 4g93 has squitter?if don't..can install the squitter together with the oil catch tank?
4) in term of bodykit..i'm now using subaru ver 3 front bumper n plan to mod subaru impreza rear bumper to wira. another plan..whether to mod nissan bluebird u13 dashboard or toyota subaru dashboard.what do u thik Ben?


Hi ben,
forget to ask u..

1) some of people says that 4g92 mivec piston same with 4g93..if i want to use mivec twincam head for my 4g93 carb for conversion from sohc it ok?
2) what high compression piston n durable con rod u suggest for 4g93 carb but change the crankshaft to 4g94?
3) is it ok to install oil cooler?

Thanks again.


Hi Syam,

I can't comment much on the FC on twin carb DCOE40 because this is very depends on the tuning and your driving style.

1. Yes but you need to cut the crankshaft abit to suit ur 4G93 and need to bore ur block to fit the piston
2. Yes.
3. Yes
4. Sorry I do not have much experience in modding bodykit and dashboard.

1. No, not the same
2. B8 piston
3. Yes.


Hi Ben,

Thanks for ur quick answer n appreciate it very much. another things to ask from u:
1) Piston B8 NA (Mazda right?) and size of it 83mm? bore size for 4g93 is need to bore around 1.5mm?how about reliability of block?
2) have u recommend another high comp piston such as wiseco and others?
3) since as u recommend B8 piston, what con rod can suit the things with crankshaft 4g94?


Hi Syam,

1. Bore 1.5mm is fine for the block and reliability of the block still consider ok.
2. If you have budget, get the wiseco 9:1 CR size 81.5mm for your car.
3. Can use 4G94.


hi ben,

need ur advise for the following:
I want to convert 4g93 sohc carb to 4g93 dohc (from injection engine)but still want to use carb.
1) any modification needed during installation of 4g93 twincam head to replace 4g93 single cam head?
2) are the extractor for 4g93 sohc carb can be fitted after change to 4g93 twincam head?
3) any benefit in term of power if I want to use high comp oversize piston(example from stock 81.5mm to higher size such as 83mm) but crankshaft still maintain the stock?is it possible and realiable? or change the crankshaft such as to 4g94 as well as bore block to use 83mm high comp piston?which one u most recommended?

Thanks Ben..from Syam

Hi Syam,

1. Make sure that is valve clearance for your piston.
2. Should be able to fit.
3. Increase of your engine capacity. Please bare in mind that changing to bigger bore piston you need to bore the cylinder. The bigger size you bore, it will cost your reliability too. For me I will try on 83mm.


hey ben
please help me on my 4g63 rvr Non turbo..any modification on this engine?can i use this guid as reference and apply it on mine?tnx need help to i want to build NA 4g63 with some budget

tnx ps renz

hi ben
any guide or help on a 4g63 RVR non turbo?

Hi bro just got a 4g93sohc ..thinking to get a b16 intake which as been modified is it ok ..

Hi Renz Acedo,

Sorry to say that I do not have the guideline for 4G62 RVR non turbo version yet. I will post it up once my friends or me got experience with it.


Hi Francis,

Have you done any modification to your 4G93 SOHC? High comp piston? Cam? If not and by running on original 4G93 SOHC 81mm flat head piston, the B16 intake is not really helpful.


hai Ben,

need ur advise n comment for 4g93 dohc with twin dcoe40 weber.the set up as following:
1) 4g94 crankshaft-to modify(cut n lighten)
2) B8 210 conrod
3) 83mm high com piston made in australia

1) use high cam..say jun or tomei spec 280++ degree


racing clutch-excedy or triniti

thanks ben

hai Ben,

what is your advise:

1) 4g93 dohc + dcoe40 twin weber (NA)

2) 4g67 + head evo-(turbo-oversize blok)

which one more power n cost?

Hi Syam,

Honestly I'm not recommend to mod the crankshaft unless you able to find a good mech for it. Based on this setting, you able to increase your torque but it will lower your rev zone. This is best for daily driven usage. May I know what is your usage of your car?



1) 4g93 dohc + dcoe40 twin weber (NA)
Good low end torque but no high rev

2) 4g67 + head evo-(turbo-oversize blok)
Better overall and cost more to maintain.


Hi to adjust valve clearance if im using 292 for my 4g93 problem is nut at the roker arm to short and is difficut to tigting...tq

Hi ben..i am driving wira se aeroback, 4G15P..sometimes during driving got the the pipe symbol appear,orange that throttle problem?or sensor?or other?
When turn iff the engine for sveral mnutes,it disappears..

Hi Ben
I'm a newbie over here so I have alot of question wan to ask you..I'm a 4g93 dohc owner and just start to play on it..what should I do on my engine?I wish even I modified on it but I still can drive long distance and daily drive too..and also costly too..i planning to use emanage blue,fuel regulatoe and also change to big piston high comp..
1.should I change my camshaft?and how many degree for daily use and long distance too
2 . how was the piston with high comp?what brand?cp or wiesco?and how many mm?81.5 or 82mm for daily use and also long distance
3.should I change my throttle body or intake manifold?
4.should I change fuel injector?
5.and how big was the exhaust system inchi 2"or2.2"or2.3" Paipe exhaust and also muffler
Please correct back me if I wrong
Thanks Ben wish you can reply me.

Hi Ben,
I just bought a Wira year 2000 with 4g93 Dohc. Due to minor leaking, Im about to do head overhaul and basic mods like replacing exhaust extractor and adjustable cam pulley. So next I plan to install an SAFC. Does these minor mods can increase HP? I have a lot in mind (lighten flywheel, oversize TB, improve ignition) but I do not know what is the best sequence of mods actually. Thanx in advance.

Hi Martin,

Orange pipe? Seem like is the exhaust sensor problem.


Hi Edwin Lim,

1. 264 degree
2. Wiseco. If budget is a constraint, get the 4G92 MIVEC pistons.
3. Yes.
4. Depends on how heavy is your mod. If mild, factory fitted injectors will be fined.
5. Depends on your mods as well. If you intended to move up further get the bigger inch size.


Hi Wanggot Duff,

My advice is,

lighten flywheel, ignition, TB, SAFC


Hi Ben
currently my lancer is running on 4g15 gdi engine, i need to swap to 4g63 gdi. do i need to change wire harness and ecu ??? and do need to change the gear box also???

Hi abaa,

It is recommended to change the entire wiring and gearbox.


Hi ben. What to do to make my 4g91 better. Now im using skunk pro series intake,evo3 throttle body. Gti extractor. 2.2 piping. Gti code e cam. Acl race bearing. Port n polished head. Mivec piston. What else to do?

Hi Asraf,

What about your management system?