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Old 15 Jul 2007, 09:35 AM   #1 (permalink)
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front mount lag

right time to tell all the facts and fiction.

first point, does a front mount cause more lag?

if mapped and modd'd correctly for it none whatso ever (well none that you can feel, and only a tiny tiny amount on the mappers laptop)

So why does the front mount sometimes get described as laggy?

short version is the MAF sensor doesn't like the front mount (should have asked exactly y not but anyhow) the combined front mount and MAF is what causes the issue.

The only other issue is with the size of the rubo, if the front mount is way way bigger in proportion to the turbo you will get some lag, but not huge amounts.


so in summary, the front mount doesn't cause lag its caused by compatability issues with the maf, do away with the maf and get a ecu that uses a map sensor and jobs a good un


hope that clears a few myths, legends and questions up
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Old 15 Jul 2007, 10:42 AM   #2 (permalink)
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would have to disagree with you slightly there Tidgy, the difference between the 2x in terms of RPM is minimal (although always a few rpm more for a front mount based on same car&spec swapping just the style of i/cooler)
however, generally speaking you will never get the same response that a top mount gives due to the extra volume of air that needs to be moved in a front mount, and also you can experience far more surge issues with a f/mount in certain applications.................

on a road car (unless there are limited options like the pre96) then i would generally recomend a good quality up-rated top mount but each to their own
** certain applications/specs require a high quality front mount **

as a slight aside one of our customers rally cars wnet down the front mount route after taking advise from another trader, it lasted one test session and then was back on the previous spec top mount..............the lack of pick-up on every corner equated to a difference of around 1-2secs/mile over a known testing venue with repeated runs / carried out with pukka custom maps for both specs

alyn
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Old 15 Jul 2007, 11:01 AM   #3 (permalink)
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With my front mount and my standard VF24 turbo etc, I dont notice lag or anything being any different to when I had the top mount fitted..

I am not running with a MAF sensor mind, so maybe that might account for some of it, but all in all, I dont see why front mounts would be described as laggy, cos I dont notice it..

Enough of the Miss Daisy jokes too before they start When the car is being driven hard, by me (ish) or someone else (mapper for example) I wouldnt say there's any lag there...

I have heard with the charge temps tho, the top mounts can be a problem. I know the mapper I use, had issues with a 22B that wanted 400bhp for example (can remember exactly) but because of the temps going into the car, it just wasnt possible, so a front mount was needed to help keep the temps down and keep the power there too.. I was shocked to hear the findings but at the same time, if the Evo's have a front mount surely there's some sense in Subaru's having them too?? Just dont understand why they dont do it as standard.. Would save us people so much money!!

EDIT - Maybe I'm just odd and wouldnt notice it!!
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Old 15 Jul 2007, 11:31 AM   #4 (permalink)
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Always find meself totally undecided as to which to go for on these threads as i`d be gutted if i lost a noticeable amount of response as love how mine drives with the std topmount,only thing for me really well 2 things is the fact that you aint getting heatsoak whilst standing with a frontmount and the fact that several ppl in other threads on other forums have said there are issues with the std scoop over 100mph actually missing the best of the airflow due to the curve of the bonnet diverting the airflow above the scoop at certain speeds.

On a private track obviously
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Old 15 Jul 2007, 12:12 PM   #5 (permalink)
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i think were gonna have to agree to disagre

i can only go on what i've been told, and said its based on back to back testing, which as far as im aware, hasn't been carried out on any other occasions, so the arguments are best guess, and different situation,

the other question would be, was tha mapping up to scratch? was it still running a maf sensor?

Quote:
Originally Posted by stockcar View Post
would have to disagree with you slightly there Tidgy, the difference between the 2x in terms of RPM is minimal (although always a few rpm more for a front mount based on same car&spec swapping just the style of i/cooler)
however, generally speaking you will never get the same response that a top mount gives due to the extra volume of air that needs to be moved in a front mount, and also you can experience far more surge issues with a f/mount in certain applications.................

on a road car (unless there are limited options like the pre96) then i would generally recomend a good quality up-rated top mount but each to their own
** certain applications/specs require a high quality front mount **

as a slight aside one of our customers rally cars wnet down the front mount route after taking advise from another trader, it lasted one test session and then was back on the previous spec top mount..............the lack of pick-up on every corner equated to a difference of around 1-2secs/mile over a known testing venue with repeated runs / carried out with pukka custom maps for both specs

alyn

tbh dave i think you need to weigh up how far your going, if your not planning to change the ecu and not going for mega power then maybe a top mount is better.

personally i'll be putting a front mount on
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Old 15 Jul 2007, 02:06 PM   #6 (permalink)
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Love impreza`s and at one time had bigger plans for mine than i have now-still want AP`s and coilovers, powerwise dont intend changing much though will be getting a remap at some stage so maybe i`ll stick with a topmount.
Cant justify spending daft money on more power i`d just buy a better car in the first place as to do it reliably the cars not worth the expense(imo)
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Old 15 Jul 2007, 03:28 PM   #7 (permalink)
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Quote:
Originally Posted by uk dave View Post
Love impreza`s and at one time had bigger plans for mine than i have now-still want AP`s and coilovers, powerwise dont intend changing much though will be getting a remap at some stage so maybe i`ll stick with a topmount.
Cant justify spending daft money on more power i`d just buy a better car in the first place as to do it reliably the cars not worth the expense(imo)
I could be selling my front mount and ECU at some point Dave... Would you like me to let you know??
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Old 15 Jul 2007, 08:36 PM   #8 (permalink)
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No mate like i say sort of content at the mo, with a remap would be more than happy i reckon-seen enough modded scoobys go pop in the last few months, after a while ya start wondering when its gonna be your turn,an im not prepared to spend that sort of money on mine unless it happens on its own anyway which is always possible so i aint out to encourage it
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Old 16 Jul 2007, 07:16 AM   #9 (permalink)
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Quote:
Originally Posted by Tidgy View Post
i think were gonna have to agree to disagre

i can only go on what i've been told, and said its based on back to back testing, which as far as im aware, hasn't been carried out on any other occasions, so the arguments are best guess, and different situation,

the other question would be, was tha mapping up to scratch? was it still running a maf sensor?

no worries, wouldn't be a forum if there was nio discussion, but i'll point out the last section of my thread..................this is simply one experience out of many, and as previously said - tested both specs back to back with custom mapping for both specs.........................

** and no MAF on either / car running GEMS

alyn
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Old 16 Jul 2007, 11:11 AM   #10 (permalink)
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Quote:
Originally Posted by stockcar View Post
no worries, wouldn't be a forum if there was nio discussion, but i'll point out the last section of my thread..................this is simply one experience out of many, and as previously said - tested both specs back to back with custom mapping for both specs.........................

** and no MAF on either / car running GEMS

alyn

tbh dont rate gems ecus at all but hey thats another issue lol
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Old 16 Jul 2007, 06:14 PM   #11 (permalink)
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think GEMS has a bad name in certain qtrs down to bad mapping/mappers....................

used for around 10yrs now and find it as good or better than other comparable systems, and easier mapping screens
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Old 16 Jul 2007, 06:40 PM   #12 (permalink)
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Quote:
Originally Posted by stockcar View Post
think GEMS has a bad name in certain qtrs down to bad mapping/mappers....................

used for around 10yrs now and find it as good or better than other comparable systems, and easier mapping screens

o right, i know a faulty gems unit got fitted to JD's car couple of weeks ago, caused right problems lol untill they realised what
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