Guys – Just installed SRT HFI last weekend and aside from the extra noise, like it so far – one little problem – I am getting a small hesitation when ease down on gas – when floor it, it goes like stink! It’s definitely faster but the (small) hesitation wasn’t there before and I have to think that something (installation or product) is at fault. I was especially careful with installation and it went well – tightened down all clamps – thinking about a vacuum leak?? Any ideas?? Anybody else experienced this?? I’ll call Mo tomorrow if I get a chance. Appreciate any ideas.

 

A couple of owners I've spoken to with SRT intakes describe this symptom also, so I think it's 'normal'. Probably a trade-off on the fuel/air curve modification the piggyback ECU does.

 

Hi Guys,
I was thinking about purchasing the SRT intake system with ECU upgrade for $575 shipped. After the installation, do you think you really got about 30 horsepower and 40 lbs of torque as they claim? That is kind of hard to believe out of an intake system. If the car gained this kind of numbers, you can definitely feel it as soon as you accelerate. Please give me your feedback regarding the SRT intake system. Thanks in advance.

 

Yeah bit, you’re right - I talked to Mo at SRT today and he confirmed that it is “normal”. Says that the “drive by wire” has a slight amount of hesitation built in and the intake compounds it. I was very aware of it today and it’s just a matter of getting used to a different feel. For those who haven’t experienced it – don’t let it deter you, it ain’t that bad – in other words, it’s worth the trade-off.

I also inquired about the woosh (like a four-barrel-without-an-air-cleaner sound) he laughed! Said they’d tried everything but an intake with a free-flow filter is going to be noisier.

Lite – my opinion is that I could care less. Not being smartass – I just mean that when someone quotes on how many horsepower/lbs. torque it “feels like” it’s subjective and many are apt to feel optimistic/positive about their product (cause it validates their decision to buy). You know that between an exhaust system and the SRT intake I could claim an additional 40hp or more, based on mfg claims. Is it there? Dunno, but I do know that there is a marked improvement in acceleration – it’s faster, noticeably faster. Was it worth $575 to me? Without a doubt - Yes.

I installed an MAF adapter and cone filter on my ’92 SC4 with Borla exhaust and while there was some improvement it was subtle, not nearly as noticeable as the SRT intake. You may be interested to know that the L-Tuned exhaust has been the car for a month or so – so I’d already become used to the acceleration before the SRT – and it was easy to feel – didn’t have to “look for it” – when you floor it the first time and think to yourself OH YEAH! Then, it’s worth it.

 

The intake is great but the hesitation is definitely there from a stop. I imagine the TC upgrade would fix this. But the extra power after you're rolling is very noticeable. Garnet's review is right on the money.

 

Hey garnet92 just wanted to say thanks on the info you sent for the intallation of the SRT HFI. It was very helpful and I must say I am loving the extra horses in my GS.

Katan

 

I remember having that hesitation with the stock intake due to that "drive by wire" setup. It just wasn't as noticeable with the factory restrictive airbox. Funny how Chevy's had that "wire" system on the Corvette for a few years & there's NO hesitation on those ( test drive in the Z06 coming next month!! ). I changed the factory ECU which was rumored to be part of the problem ( helped the starting but not the hesitation ).
Lite - Haven't spoken with anyone who got quite the gains of 30 HP/40 torque as Mo's test mule but the baseline numbers on that motor seemed lower than average so maybe it needed all the help it could get!! My dyno numbers showed a gain of 22.7 engine HP & 30.2 foot pounds of torque ( both at the same peaks as stock ) & my GS registered almost the exact factory power ratings ( using 80% driveline efficiency ). FWIW - 300.4 HP/311.2 torque. As Garnet said - there's too many variables to post "hard" dyno numbers ( air temp; mileage on engine, etc ) but if SRT claims UP TO 30 HP/40 Torque, they're well within tolerance & I'd imagine most of the users of the HFI/ECU cam back them up ( I certainly will!! ). BTW - the addition of this modification alone dropped my 0-60 times by an average of .3. Actually, it seems to help midrange & passing power the most.

 

What is your quater mile time?

Mark

 

does anyone have 1/4 mile times for their stock GS4 and then with the SRT HFI to compare? And if so what are the times?

 

In September I ran 14.42 with my Stock GS400.

Mark

 

garnet92, we have installed a few aftermarket intakes for the GS400 they all have this hesitation during WOT at low engine rpm.We believe that the slight hesitation is mainly from the larger diameter that the aftermarket intakes are so aptly built with. What's happening is that these 'larger' intake tubes have slown down the column of air before the throttle body. The OE intake has a slightly smaller diameter that was specifically designed for best power output/driveability. Remember, smaller diameter tubes convey air much more quicker than that of a larger one, but, the larger one will flow much more volume at higher rpms. This is exactly why engines gain a few horsepower with a simple free flowing air filter & intake tube. All this does is allow more air to be available for the engine to ingest, provided that you have the proper amount of fuel to atomize with this additional air. Like most have already mentioned, you just have to relearn the engines power curve & kinda 'drive-out' the hesitation. I feel that it's a small sacrifice that I can endure for the benefit of 6-10HP in the mid to high rpm ranges. Hopefully this answers your question.

 

Nicely put!!!!!!

 

lextec - EXCELLENT explanation, thanks!

 

lextec: Thanx for the explanation – it sounds reasonable and parallels one offered earlier by (either) MeanGene or Jbrady (forget which). So apparently all of the aftermarket intakes with a diameter greater than oe have the same problem (makes sense). This at least means that my SRT is no more prone to the hesitation than other brands. And you’re right – I’ve changed my driving technique to leave it in a lower gear with revs up whenever I expect to need/want “instant” acceleration. And for those who may scoff – that’s pretty much the way I drive a stick shift as well. I’m willing to pay the gas mileage penalty for the power when I want it – an I still average 15.5 mpg – all city.

BTW, are you (as your user name implies) a Lexus technician? We sure would welcome some additional objective facts about the Lexus beast – we’ve got some pretty knowledgeable members but few with access to actual Lexus maintenance procedures, policies, etc. Recognize that much will vary by dealership but some basics have to be Lexus directed. Also recognize that you may prefer to remain anonymous. Regardless, welcome to CL and feel free to offer any ideas, suggestions, etc. – we’ll appreciate it.