Intake was calculated before has been changed. Internal diameter of aluminium pipe is 3" and the rubber elbow expands from 3" to 4" near the TB. That's more than enough.

 

I don't think a 3" intake is sufficient. Testing showed that a 3.5" tube made significantly more power than 3". And that was on a stock engine.

https://www.jaguarforums.com/forum/x...results-74595/

You can hook up a vacuum (Magnehelic) gauge to your intake near the throttle body and measure the vacuum/restriction. Vacuum=restriction.

 

I plan to provide some tests when weather becomes better (now we have a lot of snow).

As for intake: do you know the diameter of stock MAF in AJ27? It's 71mm = 2.8" and part of the space is occupied by plastic sensor. That's why connecting 3" intake pipe with stock MAF is enough. The biggest restriction of the system is imho MAF.

 

The stock AJ26 MAF, as used in the above intake testing, is even more restrictive than your AJ27. Maybe it doesn't make sense why a 3.5" makes more power but the results speak for themselves. Based on before and after drag strip runs, I estimate I gained at least 30 bhp with a 3.5" intake on an otherwise stock engine.

AJ26 MAF on left vs. AJ27 on right:

 

If you want to be out of any kind of MAF restrictions , if have unused "Bad-***" 92mm MAF, BIG cone filter, pigtail and loaded tune for AJ27 with stock injectors. Plug and play. Needs just IAT sensor. EU taxed. Let me you by PM if you need it.

 

Maybe in the future. Now I have to fix the car and find the reason of engine weakness. With 2.5'' 2.2 KB pulley I have now and stock crank jag should produce healthy 500 bhp even with stock TB and MAF.

 

Steve, I have a question regarding the vacuum test you mention above. Is this the same vacuum that can be measured on OBD2 equipped cars with a standard OBD2 scanner like an ELM 327?

The reason I ask is I have measured vacuum on my S-type R using this scanner and saw only 1" of vacuum at WOT. From memory, at idle its around 19-20". Is this an accurate way of testing intake vacuum for restriction? I would assume 1" is quite low and the stock intake is more than enough at my current power.

My car has a 1.7 Autorotor twin screw with a 2.16" upper pulley and stock crank pulley. It really doesn't need anymore power, but I was just curious whether you (or anyone else) thinks more power is available from using a larger MAF/intake with the vacuum I'm seeing at WOT? I should add that I have the stock 75mm TB, 3.5inch intake pipe down to stock MAF and a K&N panel filter.

 

JagSTR2004,

I'm not familiar with measuring vacuum with a scanner or how accurate it is. Is the sensor located at the intake elbow between TB and supercharger? If accurate, 1" hg is indeed low.

I used a Dwyer Magnehelic pressure differential guage and tee'd into a vacuum line coming off the inlet elbow, after the TB. Where ever you hook up the gauge to along the intake will give you the vacuum reading up to that point. You can test just a TB or MAF by getting readings before and after that location, etc.

For example, my restriction measured after the stock TB was 130 inH2O (twin screw, 3.5" intake, stock MAF and TB). After boring the TB, the vacuum dropped to 40-45 inH2O and I gained a few psi of boost.

 

130 inches of water is -4.7 PSI. Real terrible result. If vacuum dropped to 45inH2O ~ 1.6PSI that means you gained 3.1 PSI of boost.

 

Yes, I believe the sensor which reads vacuum on the STR is the MAP sensor which is located near the intake elbow between the TB and the supercharger. It reads just like a mechanical one which makes me think it's reasonably accurate, I.e. the more throttle you give the less vacuum you have. Also if I disconnect a vacuum line it decreases at idle.

I converted your vacuum from inches of water to inches hg and boring definitely made a huge difference taking it down from 9.5 to 4.5"hg. You probably have way more restriction than me due to the larger displacement 2.6 supercharger and think there's more boost left to gain with less restriction.

Thanks for your help.

 

I would double check it with gauge teed to bypass actuator hose.

 

Will do Przemek. What I really ought to do is get in on the dyno with such a guage attached. Let us know how you get on fixing your set up, I'm sure it'll be a beast once sorted.

 

I managed to log the car today using chinese launch x431. There is one fault in ECM which might be important: P0101 MAF Circuit Range/Performance.

Bingo?

 

My humble guess is that, if you don't have a dirty/bad MAF, you're probably pegging it at high revs which is causing the code. Have you monitored the g/s at WOT?

 

What do you mean saying 'pegging in at high revs'?

Unfortunately roads are now to slippery for testing anything at WOT.

 

What I meant by "pegging" is that with the 2.5" pulley on the 2.2 KB, you've probably maxed out your stock MAF. The incoming air has exceeded the maximum possible voltage for the MAF and to prevent a lean condition from the excess unmetered air, the ECU goes into restricted performance. If this is what is happening, you will need a larger 85mm or 90mm MAF to solve the problem. This is just my theory of what I think is the problem, testing at WOT should make it obvious.

 

Will check MAF readings.

I'm comparing my car with SteveM's XJR. He has stock TB, MAF as well and with 3.0" KB 2.6 pulley his car doesn't throw faults. KB 2.2 equipped with 2.5" pulley will push comparable amounts of air as KB 2.6 with 3.0" pulley.

Moreover I had restricted performance fault (P0101) on highway while crusing with low speed.

 

My old setup hit max 400g/s well before 6K rpm even with 3.25" upper / 6.65" lower . No codes. Just one blown engine

 

6.65'' lower? Was it custom machined pulley?

 

I have used stock 4.0, 6.65" and 6.93" lower pullies and 3", 3.25" and 3.5" uppers.