Introducing the JHM 4.2L V8 Intake Manifold upgrade for the B6/B7 S4 and C5-allroad 4.2L.
*NOTE: AS OF 8/23 WE NO LONGER OFFER A CORE EXCHANGE FOR THE INTAKE MANIFOLDS DUE TO THE LACK OF QUALITY CORES AVAILABLE. WE WILL NOW ONLY MODIFY THE INTAKE MANIFOLDS THAT YOU SEND IN TO US. IF YOU AREN’T ABLE TO HAVE YOUR VEHICLE DOWN WHILE YOU WAIT, YOU ARE WELCOME TO SOURCE YOUR OWN CORE TO SEND TO US. POWDERCOAT OPTIONS HAVE ALSO BEEN REMOVED *
Expect 4 to 8 weeks for the manifold to be ready and complete, they are coming in and getting modified steadily as fast as possible.
 
We started on this project in late 2008 to maximize the power output of the B6/B7 S4 and C5-allroad 4.2L without cylinder head porting (coming soon as well) or cams, basically with just bolt on parts. Finally after tons of hard work and several prototypes we have the results we were looking for out of an Intake Manifold to finally fully maximize these engines from just bolt on parts.
Why just re engineer a stock intake manifold?? We chose to re engineer a stock intake manifold to keep the exact OEM factory look while retaining the dual plenum manifold design which maximizes low end torque and high rpm horsepower. Most of our modifications were done to improve high rpm horsepower without sacrificing low end torque in any way. This also keeps costs down for our customers since the S4 is a car that didn’t have very high production numbers. We also found during dyno testing that we lost 55 ft lbs of torque at the wheels (over 70 crank tq) when disabling the dual plenum flap design. This ruled out a complete fabricated replacement that was a single plenum design since losing torque kills throttle reponse for day to day driving. This manifold brings the best of both worlds, stock or better low end torque and more high rpm power with an OEM look.
DRAGSTRIP AND DYNO PROVEN!
At the dragstrip – We ended running a best of 12.70 @ 111mph all motor (with our new intake manifold and our headers) which was a strong improvement over our previous best of 12.97 @ 109mph (with a stock intake manifold and stock exhaust manifolds). Both of these runs were with JHM Tuning, JHM Lightweight crank pulley, JHM intake spacers, JHM Lightweight Flywheel and JHM Performance Clutch. You may wonder about the affect the headers had on this track time, well the headers have been proven to only help with low RPM torque under 4000 rpm due to restrictions in the stock cylinder head. When racing the quarter mile we shift at 6500 rpm so the engine never gets below 5000 rpm which is where our intake manifold shines and allowed us to pick up 2 mph. The headers extra torque actually made our launch harder since the car had a tendency to spin the tires more easily than before. This torque is wonderful on the street but a handful to get a good clean launch. The bottom line is that with all the JHM bolt ons on our car the car is a lot more powerful than stock and has set every quarter mile record for all Motor S4s while being faster than many other company’s supercharger kits.
On the dyno – On 91 octane gas here in California with our 05 manual transmission car that is equipped with our headers, tune, other bolt onse we saw 16 whp gains (22 crank hp). We did 3 baseline runs on the dyno confirming a constant intake manifold temp of 110f to 115f. We then replaced the intake manifold with our unit and then warmed the manifold up to the same 110f to 115f. We saw a consistent gain pull after pull. With our car being equipped with headers we saw a 5 ft lb of torque at the wheels gain (7 crank torque). We also did testing with a 06 Automatic transmission car that was equipped with our headers and cats along with our tune and other bolt ons. This car gained as high as 17whp (23+ crank hp) and as high as a 6 ft lb of torque at the wheels gain (8 crank torque). After this testing with 2 JHM header cars and the cylinder heads being the only cork we continued testing and decided to do a car that had high rpm power limiting piggie pipes (due to the use of 2.125″ piping and stock main cats). With this car on 91 octane we saw 10+whp (13 crank hp) gains and identical torque as stock. This was great news for our headers seeing that they helped out our JHM intake manifold in gaining more torque than the stock manifold did. This also gave us a bottom line to let you the customer know the full story. If you are wondering about cars that do not have headers but have aftermarket downpipes we have seen as high as 15whp with those setups as well. So this manifold performse very well with any exhaust configuration. The only exhaust we didn’t test was totally stock downpipes since the restrictive main cats would defeat the purpose of our intake manifold by restricting the air coming out of the engine. We have also had several customers on the East Coast do testing as well and based on their dyno sheets 93 octane cars should see the same if not better numbers than we did on 91 octane.
PHOTO OF THE HEAT SHIELD OPTION WE OFFER TO DEFLECT HEAT GENERATED BY THE ENGINE BLOCK. This is sold separately on our site as SKU DEI-010392.
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PHOTO OF THE INTAKE SPACER OPTIONS.
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DETAILS AND OPTIONS
Details
Fits all B6/B7 S4s and C5-allroad 4.2L with the 40 valve 4.2L V8. (Does NOT fit B7 RS4)
Includes
1 – JHM Modified Intake manifold (Port work, internal re engineered shaping and better flowing flap to name a few items done to this manifold).
1 – JHM Ported Throttle Body
NOTE: If you do NOT select intake spacers you will need to by Q2 of 077129717Q intake manifold gaskets to do the install. Just search for that PN to purchase in our search box above.
RECOMMENDED: -INTAKE SPACERS – Our intake manifold has the ports fully matched to the intake gasket size which is a little bigger than the factory head casting. If you already have JHM straight through intake spacers then there will be a slight lip that this extra air from the new manifold will hit and will cause tumbling which may hurt hp by 1 to 2 hp. If you are looking for maximum performance with this manifold and stock heads there are 2 options. JHM Tapered gasket matching spacers that will make the air transition smoothly to the head or the JHM straight spacers that we would recommend that the heads are gasket matched to eliminate the lips and tumbling (this process can take 5 to 8 hours to be done properly on the car, we recommend this is done by a professional. NOTE: We recommend getting the tapered spacers since with our testing, due to restrictions further inside the cylinder head the tapered spacers make the same HP and TQ if not more than the gasket matched heads. You can also choose no spacers if you have our straight spacers already or do not want to run spacers at all. If you only want gaskets search for PN 077129717Q on our site add qty 2 to your order.
AVAILABLE FOR PURCHASE SEPARATELY:
HEAT SHIELDING – Due to the fact that the intake manifold sits far down in the engine valley which is a large source of heat we recommend having us install self adhesive shielding that keeps the intake manifold cooler, thus allowing the car to make more power consistently. With the intake manifold staying colder due to this shielding intake temps are lowered and as we all know colder air is denser, therefore more air gets into the motor and you make more power. This is sold separately on our site as SKU DEI-010392.
NOTE: Like ALL aftermarket modifications unless a CARB E.O number is obtained, this intake manifold is technically not legal in the state of California and other states (check your state laws for details). It is for offroad use only. However this Manifold has an exact stock appearance and does not affect tailpipe emissions adversely in any way.
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