stux2004
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A typical question - how do I make genuine gains and power from my Accord Type R?
This guide describes 'stages' of modification, we start at the top with basic and work down to more comprehensive modifications. The gains represent the typical peak power gain, often members see more power on a back-to-back dyno run but for this article we’ll use more conservative estimates.
Please remember you can also lose power in certain areas with modifications – the only true way to iron these out is with fuel AFR mapping or a standalone ECU.
INTAKE
Stock: The standard intake is a well developed and has to be for a ~97BHP per litre N/A engine, it does however balance performance with comfort i.e. it's made to reduce specific harmonics in the rev range and excessive induction noise.
If induction noise doesn’t concern you there are several options at your disposal.
Panel Filter (+3-5HP/+3lb tq): the most cost effective and accessible mod for any member. Simple purchase and ‘drop-in’ a panel filter from one of the major manufacturers such as K&N and you’ll gain some added throttle response, a little more power across the rev range and a slightly deeper induction note. A very cost-effective solution and in most cases cheaper than the original Honda filter element.
Short Ram (No consistent gain): In most cases the short ram intakes offer two things, lots of noise and LESS power. The problem with short rams is they sound great, typically offer crisp throttle response due to their short intake tract but drawn hot engine from the bay reducing intake efficiency. Hot air is less dense than cool, simply put you need more of it to burn your fuel.
Long Intake/CAI (+5HP/ + 5lb tq): A ‘Cold Air Intake’ moves the air filter away from the engine area to remove the problem of hot air being drawn, this in-turn can improve the efficiency of the combustion and power gains are often seen across the range. The downside with a longer intake tract is the slight numbing of throttle response, the longer intake has a higher volume of air to move and at lower velocity this can cause turbulent air flow.
A favourite amongst forum members is the K&N Typhoon which was designed specifically for the ATR by K&N, it’s worth mentioning however the induction note is very loud and strong – people will know when you’re on the throttle!
ITB/Throttle Bodies (+20-50HP/+15-40lb tq): A forum member named Sandy has run ITBs on his H22A7 with great results, strong torque across the power-band and a bump in peak power. This modification however requires a lot of custom work and is a tight fit in the engine bay. You should only consider this modification if you’re prepared to modify the firewall and spend time customising products to suit your requirements. The plus side is a wonderful induction note, crisp and instant throttle response with very drivable torque. Suited mainly for track and/or race cars.
Forced Induction (+30-400HP): The expensive route of a supercharger or turbo on a stock H22A7 will reward you with ample power gains, in turn it will potentially reduce engine longevity and reliability. The complexity and quality of the tuning work carried out make or break (literally) this mod. A well tuned and mapped turbo could easily net you a 30% gain on a stock engine whilst remaining daily drivable and reliable.
Things to consider are cost, heat and AFR (detonation). Search the forum for detailed topics on these matters.
EXHAUST
Stock: to comply with sound and emission regulations the standard Accord Type R exhaust system can be considered restrictive.
Stage 1 Cat-back system (+5HP): A stainless cat-back system, from the catalytic converter on, is a typical modification on most enthusiasts cars. A good quality 2.25-2.5" system will often open up the car in VTEC.
A simple analogy would be less exhaust gas flow requires a smaller space than high gas flow, thus the wider the space the more gas required to fill it. Obviously the gas flow at a given rpm on a stock engine will be the same regardless of exhaust, going straight to a wide free-flow exhaust slows the gas at lower rpms and as a result can affect the emptying of the combustion chambers giving the sense of a flatter or 'duller' power application in lower rev ranges.
On the flip-side the stock exhaust doesn't flow enough for the higher VTEC ranges and so with a wider system the gases are able to flow faster and make use of the space as volume increase.
This is the reason you'll often see a 3" pipe used on a turbo engine, purely for the fact gas flow is substantially increased.
Off the shelf and custom items range from £300-600+.
Stage 2 De-Cat and cat-back Exhaust (+10HP): De-cat exhaust system with o2 spacer. This modification causes a problem at MOT time in that it’s likely you’ll fail the emissions test, however this doesn’t stop you keeping the Cat and swapping it over for the test.
A de-cat or ‘testpipe’ is roughly £60-100 and should come with an o2 sensor spacer. Without a spacer the o2 will throw an error code as it detects an increase in exhaust flow, the spacer tricks the sensor by removing it from the direct flow.
Another option is to install a high-flow Cat, this is a custom option requiring the correct flanges to be welded to the high-flow Cat. Typically this mod will set you back several hundred pounds but will allow you to pass your MOT emissions without issue.
The benefits of both are reducing restriction by increasing exhaust flow and hence achieving higher power figures particularly in VTEC.
Stage 3 Exhaust Manifold, de-cat and exhaust (+15HP): A complete setup with a stainless steel exhaust manifold, de-cat and exhaust system - the most expensive option.
The common consensus is that the ATR has a pretty good exhaust manifold from factory, and that it is hard to better it.
Upon closer inspection, the OEM manifold has deceptively large runners, they look larger than they are. coupled with mass produced stamped collectors, and a very restrictive 2-1 section, improvements can be made across the board.
There are a number of ATR specific exhaust manifolds now available, custom built and dyno proven by Vtecdirect and Solid Fabrications.
The biggest misconception is that 4-2-1 branch manifolds give better midrange whereas 4-1 manifolds give peak gains; the design, length, width, stepping and collector side determine where and how power is made. You should look at the dyno results of the different manifold to see what power characteristics you prefer.
A well designed manifold with full system will give you the biggest gains across the whole rev range, in some cases these gains are quite evident.
This guide describes 'stages' of modification, we start at the top with basic and work down to more comprehensive modifications. The gains represent the typical peak power gain, often members see more power on a back-to-back dyno run but for this article we’ll use more conservative estimates.
Please remember you can also lose power in certain areas with modifications – the only true way to iron these out is with fuel AFR mapping or a standalone ECU.
INTAKE
Stock: The standard intake is a well developed and has to be for a ~97BHP per litre N/A engine, it does however balance performance with comfort i.e. it's made to reduce specific harmonics in the rev range and excessive induction noise.
If induction noise doesn’t concern you there are several options at your disposal.
Panel Filter (+3-5HP/+3lb tq): the most cost effective and accessible mod for any member. Simple purchase and ‘drop-in’ a panel filter from one of the major manufacturers such as K&N and you’ll gain some added throttle response, a little more power across the rev range and a slightly deeper induction note. A very cost-effective solution and in most cases cheaper than the original Honda filter element.
Short Ram (No consistent gain): In most cases the short ram intakes offer two things, lots of noise and LESS power. The problem with short rams is they sound great, typically offer crisp throttle response due to their short intake tract but drawn hot engine from the bay reducing intake efficiency. Hot air is less dense than cool, simply put you need more of it to burn your fuel.
Long Intake/CAI (+5HP/ + 5lb tq): A ‘Cold Air Intake’ moves the air filter away from the engine area to remove the problem of hot air being drawn, this in-turn can improve the efficiency of the combustion and power gains are often seen across the range. The downside with a longer intake tract is the slight numbing of throttle response, the longer intake has a higher volume of air to move and at lower velocity this can cause turbulent air flow.
A favourite amongst forum members is the K&N Typhoon which was designed specifically for the ATR by K&N, it’s worth mentioning however the induction note is very loud and strong – people will know when you’re on the throttle!
ITB/Throttle Bodies (+20-50HP/+15-40lb tq): A forum member named Sandy has run ITBs on his H22A7 with great results, strong torque across the power-band and a bump in peak power. This modification however requires a lot of custom work and is a tight fit in the engine bay. You should only consider this modification if you’re prepared to modify the firewall and spend time customising products to suit your requirements. The plus side is a wonderful induction note, crisp and instant throttle response with very drivable torque. Suited mainly for track and/or race cars.
Forced Induction (+30-400HP): The expensive route of a supercharger or turbo on a stock H22A7 will reward you with ample power gains, in turn it will potentially reduce engine longevity and reliability. The complexity and quality of the tuning work carried out make or break (literally) this mod. A well tuned and mapped turbo could easily net you a 30% gain on a stock engine whilst remaining daily drivable and reliable.
Things to consider are cost, heat and AFR (detonation). Search the forum for detailed topics on these matters.
EXHAUST
Stock: to comply with sound and emission regulations the standard Accord Type R exhaust system can be considered restrictive.
Stage 1 Cat-back system (+5HP): A stainless cat-back system, from the catalytic converter on, is a typical modification on most enthusiasts cars. A good quality 2.25-2.5" system will often open up the car in VTEC.
A simple analogy would be less exhaust gas flow requires a smaller space than high gas flow, thus the wider the space the more gas required to fill it. Obviously the gas flow at a given rpm on a stock engine will be the same regardless of exhaust, going straight to a wide free-flow exhaust slows the gas at lower rpms and as a result can affect the emptying of the combustion chambers giving the sense of a flatter or 'duller' power application in lower rev ranges.
On the flip-side the stock exhaust doesn't flow enough for the higher VTEC ranges and so with a wider system the gases are able to flow faster and make use of the space as volume increase.
This is the reason you'll often see a 3" pipe used on a turbo engine, purely for the fact gas flow is substantially increased.
Off the shelf and custom items range from £300-600+.
Stage 2 De-Cat and cat-back Exhaust (+10HP): De-cat exhaust system with o2 spacer. This modification causes a problem at MOT time in that it’s likely you’ll fail the emissions test, however this doesn’t stop you keeping the Cat and swapping it over for the test.
A de-cat or ‘testpipe’ is roughly £60-100 and should come with an o2 sensor spacer. Without a spacer the o2 will throw an error code as it detects an increase in exhaust flow, the spacer tricks the sensor by removing it from the direct flow.
Another option is to install a high-flow Cat, this is a custom option requiring the correct flanges to be welded to the high-flow Cat. Typically this mod will set you back several hundred pounds but will allow you to pass your MOT emissions without issue.
The benefits of both are reducing restriction by increasing exhaust flow and hence achieving higher power figures particularly in VTEC.
Stage 3 Exhaust Manifold, de-cat and exhaust (+15HP): A complete setup with a stainless steel exhaust manifold, de-cat and exhaust system - the most expensive option.
The common consensus is that the ATR has a pretty good exhaust manifold from factory, and that it is hard to better it.
Upon closer inspection, the OEM manifold has deceptively large runners, they look larger than they are. coupled with mass produced stamped collectors, and a very restrictive 2-1 section, improvements can be made across the board.
There are a number of ATR specific exhaust manifolds now available, custom built and dyno proven by Vtecdirect and Solid Fabrications.
The biggest misconception is that 4-2-1 branch manifolds give better midrange whereas 4-1 manifolds give peak gains; the design, length, width, stepping and collector side determine where and how power is made. You should look at the dyno results of the different manifold to see what power characteristics you prefer.
A well designed manifold with full system will give you the biggest gains across the whole rev range, in some cases these gains are quite evident.
